I have ISA and IIS on the same box (Windows 2000 Server SP3, ISA SP1, IIS 6).
This configuration is the same since 2 years and works fine ... since 15 days !
All the machine in the LAN have always their internet access without
problem, but on ISA/IIS server no more access is available (web, FTP,...)
and our site (Web, FTP) does not work any more.
The rules seems to be always good.
Bit Defender has found no virus.
The Norton Fix Codered has not detected a problem.