More infos:

i'm able to use the webgrid in sharepoint designer setting trust level to Full, but when i try to see tha aspx page that holds the webgrid control i get the same error.

I also have a js error:

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; InfoPath.2; .NET4.0C; .NET4.0E)
Timestamp: Mon, 21 Dec 2009 13:47:42 UTC

Message: 'null' is null or not an object
Line: 9
Char: 34130
Code: 0
URI: http://vmoss2007/ISRes.axd?F/ISCore.js/305000750

do you understand what i miss?

the axd mapping should be good because if i type

http://server/site/ISRes.axd?G/wg_filter.gif

i correctly get an image

From my experience using our controls in WebPart, you will need runtime license key. The runtimelicense key will be provided after purchasing our component.

The javascript error is commonly caused when you are missing WebUI Framework dll in your project bin folder. Please copy the ISNet.dll, ISNet.WebUI.dll, and ISNet.WebUI.Resources.dll to your project bin folder.

Thanks for your response.

I launched a program for fixing the registry for x64 machines, i don't know how or why but it worked and i solved license issues.

I also discovered that js error was due to lack of scripts in general, but your grid works fine in a new aspx page, so the problem is in my code, not in WebGrid or SP :)