I use the same build number (build 219) of WebCombo.NET 4.0 and WebUI.NET Framework 3.0 build 751 on my end and was unable to repro the issue on my end.

Please check following list in order to determine what may cause the issue.

• Please ensure that you use the latest build number of WebUI.NET Framework 3.0 (build 751).
• Please check whether the issue persists on any sample files of WebComboSamples project or not. You’ll need to update the dll files inside this project bin folder.
• If the issue doesn’t persist on WebComboSamples project, is it replicable using a simple sample of WebCombo? If it does, could you please send the sample to us to be investigated further?