My client recently installed a magic device from Juniper that apparently replaced their old Cisco network load balancer (NLB). At about the same time, we installed a hotfix to address a workflow problem.
A day or two later, we noticed a problem when we accessed the shared service provider (SSP). We could get to it, but we would be challenged for a user ID and password many times on each page. This didn’t happen with the main portal app, nor central administration. Naturally, we didn’t know which of the two (Juniper or hotfix) would be the issue, though I strongly suspected the hotfix, figuring we had not installed it quite right.
It turned out that Juniper had some kind of compression setting. One of the robed figures over in the network group turned that setting off. That solved our problem.
This is not the first time that compression has been the root cause of a SharePoint problem for me. IIS compression adversely affected a 3rd party tool from the good people at The Dot Net Factory for IE 6 browsers (IE 7 browsers worked without difficulty).
So, add "compression" to the hazards list.