Hello, I am not sure if you guys have this problem... but here is the deal..
This is happening when hosting a WebEx session AND I am sharing an application..
If I resize/move the shared app (e.g. Internet Explorer), the computer COMPLETELY locks up! Even the mouse locks up.. .

I have to force power off and restart..
Has anybody seen this?

NOTE: This is happening with both the WebEx Java client and the WebEx ActiveX control on both IE7 and latest Firefox...

OK, I am answering my own question.. maybe it will be helpful for others..
When you resize a shared application in a WebEx session, your computer will completely lock up.

This is a Vista (Win2008 Svr) issue. There is a 'hotfix' available from Microsoft, but you have to go thro many hoops to get to it..
http://support.microsoft.com/kb/954436

The WebEx knowledge base talks about this
http://support.webex.com/SelfServiceWeb/SelfServicePortal.portal?_nfpb=true&kbViewArticle_actionOverride=%2Fportlets%2FViewArticle%2FcurrentArticle&_windowLabel=kbViewArticle&kbViewArticlereturnTo=kbResults

Thanks for posting this response. Yours was the only explanation and an excellent one. I had to do two reboots today alone. Hopefully, this hotfix will correct the problem. I can't thank you enough!

Just my two cents...

According to the Knowledgebase Article there, "This problem occurs because of an error in the Win32k.sys file."

If a system driver has an error, why the heck isn't it included in Automatic Updates?