ok
the first thing to check are your settings
go to
tools | internet options | advanced
(easies here is just to reset to defaults)
then still on the on the internet options panel go to security and - unless you have a particular reason for using other settings ... go for medium high (the default) on the internet options)
see what happens
also .... if you haven't already - consider upgrading to ie7
if that fails
try downloading firefox from
http://portableapps.com/news/2007-12-05_-_fire fox_portable_2.0.0.11
it's fully self contained .... so you don't have to risk your existing settings - and will prove a point (if all else fails).