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
