Might be the same one as for Explorer, the non-Internet file manager. Anyway, that's my best guess; look around a bit in the Control Panel and so on, to see if you have different settings anywhere.

Oh, and were there any other updates besides the OS -- is it the same version of IE? (We use 5.5 at work, and it would probably break pretty much everything we use to update to 6.0 -- we're so far into Java, you'd think it's Sun I'm working at.)