Barbara, I am having the same problem, did you ever get a solution?

When I ping localhost the reply comes back from ::1 where it should have come back from 127.0.0.1 - so it seems as though something has disassociated localhost from the loopback setting, despite what the HOSTS file says.

I suspect this started happening after I loaded a patch for SP2 that was desined to prevent malicious use of the brower to run exe's - can't remember the exact wording...