I have created a WebPaneManager with a standard side template that has a WebExplorerPane in its smaller left pane.  The problem is when a user does a mouse-over of the splitter for the WebPaneManager, the WebExplorerPane disappears!  Here is the code:

<ISWebDesktop:WebPaneManager ID="WebPaneManager1" runat="server" Height="100%" 
            Width="100%" ViewStateItems="BehaviorAndCollection">
            <RootGroupPane GroupType="VerticalTile" Name="RootGroupPane" 
                GroupPaneHeaderVisible="Yes" Text="Task Tracker" TextAlignment="Center" 
                UseRelativePositioning="True">
                <Panes>
                    <ISWebDesktop:WebPane Name="Nav" Text="Navigation" 
                        ContentMode="UseInlineContent" 
                        InfoText="Bring up tasks or get general help information" 
                        Width="Custom" WidthValue="155px" AllowCollapse="No" AllowResize="Yes" 
                        InfoTextAlignment="Left" UseRelativePositioning="True">
                        <ContentTemplate>
                            <ISWebDesktop:WebExplorerPane ID="WebExplorerPane1" runat="server" 
                                Height="100%" Width="150px" RenderAsListBox="True" 
                                RenderMode="RoundCorner" ViewStateItems="BehaviorAndCollection">
                                <FrameStyle BackColor="White" BackColor2="224, 224, 224" BorderColor="Silver" 
                                    BorderWidth="1px" GradientType="Vertical">
                                    <Padding Bottom="10px" Left="10px" Right="10px" Top="10px" />
                                </FrameStyle>
                                <PaneItemSettings>
                                    <ItemStyle>
                                    <Normal Cursor="Hand" Font-Names="Tahoma" Font-Size="8.25pt" Overflow="Hidden">
                                        <Padding Bottom="3px" Left="6px" Right="6px" Top="3px" />
                                    </Normal>
                                    <Over BackColor="WhiteSmoke" BaseStyle="Normal">
                                    </Over>
                                    <Active BackColor="#C0C0FF" BaseStyle="Normal" BorderColor="#0000C0" 
                                        BorderStyle="Solid" BorderWidth="1px" Font-Bold="True">
                                    </Active>
                                    </ItemStyle>
                                    <ItemsContainerStyle BackColor="White" Font-Names="Tahoma" Font-Size="8.25pt">
                                        <Padding Bottom="4px" Left="4px" Right="4px" Top="4px" />
                                    </ItemsContainerStyle>
                                </PaneItemSettings>
                                <PaneSettings>
                                    <BarFontStyle>
                                        <Normal Font-Bold="True" Font-Names="Tahoma" Font-Size="8.25pt">
                                        </Normal>
                                        <Over ForeColor="Gray">
                                        </Over>
                                    </BarFontStyle>
                                    <SpecialBarFontStyle>
                                        <Normal Font-Bold="True" Font-Names="Tahoma" Font-Size="8.25pt" 
                                            ForeColor="White">
                                        </Normal>
                                        <Over ForeColor="Gainsboro">
                                        </Over>
                                    </SpecialBarFontStyle>
                                    <BarStyle>
                                        <Normal BackColor="WhiteSmoke" BackColor2="211, 211, 211" Cursor="Hand" 
                                            Font-Bold="True" Font-Names="Tahoma" Font-Size="8.25pt" Overflow="Hidden" 
                                            OverflowX="Hidden" OverflowY="Hidden">
                                        </Normal>
                                        <Over ForeColor="Gray">
                                        </Over>
                                    </BarStyle>
                                    <SpecialBarStyle>
                                        <Normal BackColor="Gray" BackColor2="0, 0, 0" Cursor="Hand" Font-Bold="True" 
                                            Font-Names="Tahoma" Font-Size="8.25pt" ForeColor="White" Overflow="Hidden" 
                                            OverflowX="Hidden" OverflowY="Hidden">
                                        </Normal>
                                        <Over ForeColor="Gainsboro">
                                        </Over>
                                    </SpecialBarStyle>
                                    <BarFrameStyle BorderColor="LightGray" BorderStyle="Solid" BorderWidth="1px">
                                    </BarFrameStyle>
                                </PaneSettings>
                                <Panes>
                                    <ISWebDesktop:WebExplorerBar CaptionDisplayMode="TextAndImage" 
                                        Image="./Images/Outlook-32.gif" ImageSize="32px" Name="ExplorePane1" 
                                        Text="Help" ToolTip="This section provides quick tips on using the site">
                                        <PaneItems>
                                            <ISWebDesktop:WebExplorerBarItem Image="./Images/outlook-16.gif" 
                                                Name="itm_Help" Text="Help" />
                                            <ISWebDesktop:WebExplorerBarItem Image="./Images/outlook-16.gif" 
                                                Name="itm_Status" Text="Status" 
                                                ToolTip="Gives the statuses of the processes used by the real-time interface" />
                                        </PaneItems>
                                        <ItemSettings DisplayMode="TextAndImage">
                                        </ItemSettings>
                                    </ISWebDesktop:WebExplorerBar>
                                    <ISWebDesktop:WebExplorerBar Image="./Images/mycust-32.gif" ImageSize="32px" 
                                        Name="ExplorePane2" Text="DME" ToolTip="Section for DME-related tasks" 
                                        CaptionDisplayMode="TextAndImage">
                                        <PaneItems>
                                            <ISWebDesktop:WebExplorerBarItem Image="./Images/mycust-16.gif" 
                                                Name="itm_DMEPending" Text="DME Pending" 
                                                ToolTip="For DME questionnaires requiring response" />
                                            <ISWebDesktop:WebExplorerBarItem Image="./Images/outlook-16.gif" 
                                                Name="itm_DMECharges" Text="DME Charges" 
                                                ToolTip="For invalid DME-related charges" />
                                        </PaneItems>
                                        <ItemSettings DisplayMode="TextAndImage">
                                        </ItemSettings>
                                    </ISWebDesktop:WebExplorerBar>
                                </Panes>
                            </ISWebDesktop:WebExplorerPane>
                        </ContentTemplate>
                    </ISWebDesktop:WebPane>
                    <ISWebDesktop:WebPane Image="./Images/WebDesktopManager-64.gif" Name="Detail" 
                        Text="Detail" TextAlignment="Center">
                    </ISWebDesktop:WebPane>
                </Panes>
            </RootGroupPane>

<SplitterStyle>
<Normal BackColor="#BDD9FE" BackColor2="101, 144, 204" GradientType="Vertical"></Normal>

    <Over BaseStyle="Normal">
    </Over>

<Active BaseStyle="Normal" BackColor="Black"></Active>
</SplitterStyle>

<PaneSettings GroupPaneHeaderVisible="Yes" TextAlignment="Center">
<ContainerStyle Overflow="Auto" OverflowY="Auto" OverflowX="Auto" BackColor="White" 
        BorderColor="#6593CF" BorderStyle="Solid" BorderWidth="1px" Font-Names="Tahoma" 
        Font-Size="8pt" ForeColor="Black">
<Padding Top="4px" Left="4px" Right="4px" Bottom="4px"></Padding>
</ContainerStyle>

<HeaderMainStyle BackColor="#D6E7FF" BorderColor="#6593CF" BorderStyle="Solid" 
        BorderWidth="1px" Font-Bold="True" Font-Names="segoe ui,arial" Font-Size="10pt" 
        ForeColor="#15428B" 
        BackgroundImage="url(/CommonLibrary/Images/WebDesktop/np_o7_header.gif)">
<Padding Top="4px" Left="4px" Right="4px" Bottom="4px"></Padding>
</HeaderMainStyle>

<HeaderSubStyle GradientType="Vertical" BackColor2="255, 255, 255" 
        BackColor="#D6E7FF" BorderColor="#6593CF" BorderStyle="Solid" BorderWidth="1px" 
        Font-Names="segoe ui,tahoma" Font-Size="8pt" ForeColor="#15428B">
<Padding Top="4px" Left="4px" Right="4px" Bottom="4px"></Padding>
</HeaderSubStyle>

<InfoTextStyle Font-Names="Tahoma" Font-Size="8pt" ForeColor="White"></InfoTextStyle>
</PaneSettings>

<FrameStyle BackColor="#BDD9FE" BorderColor="#6593CF" BorderStyle="Solid" BorderWidth="1px" 
                ForeColor="White" BackColor2="101, 144, 204" GradientType="Vertical">
<Padding Top="4px" Left="4px" Right="4px" Bottom="4px"></Padding>
</FrameStyle>
        </ISWebDesktop:WebPaneManager>