It's a shame that I often find their IT staff missing. Is yours missing too?
Although this topic might sounds "fundamental stuff", we still see many luggage where DNS is the wrongdoer. There are cases where DNS is not answer properly, not correctly configured on ISA Server and in some cases the DNS Server is really down (easy one to fix it J). The fact that matter is that if your DNS gets below par, ISA will be ill too. ISA Server rely as a core component on name resolution, although ISA Server has its own DNS cache that runs under the firewall service process context (wsprsrv.exe), ISA is still using the OS DNS client as well.