I can get here, but no one at work using our proxy can seem to get to MSDN.
Our Network Administrator has no clue. He said if I could figure it out, he'd fix it. He thinks it is because the ISA Server is too old to understand Microsoft's newer HTML technology.
Are there any errors in the ISA logs? ISA should be able to handle these websites.
This is normally a DNS problem.
If it is just this site, it may be that the address to MSDN is registered incorrectly in a HOSTS file or the internal DNS.
For other possibilities see: http://forums.isaserver.org/m_2002006838/mpage_1/key_/tm.htm#2002006915