Sounds familiar? Interesting though is that in this case it was not an ISA issue (really??? J) and was actually fixed using the solution below from IE Team:

http://blogs.msdn.com/askie/archive/2009/07/17/slow-performance-in-internet-explorer-8-after-installing-the-skype-v4-1-application.aspx

 

One more issue that is not caused by ISA Server…and counting.