I have this problem too and it's driving me crazy.

I use firefox 3.5.7 and every time I try to download a file it wants to download a file called clear.gif
even the latest posts including files won't let me download, it does not matter if I click on the link or right click and "Save as" it does not work.
this forum has never been good since the update, it was much better before, I have even had PMs from other members that just did not arrive.
I also find it very slow to browse the forum. Sometimes the old saying "If it ain't broke, then don't try to fix it" is very true.