I took a quick search to see if this topic had already been addressed, but I did not see it, so here we go...
Using IE7 on fully patched XP, if I go to the forums (when not logged in), I cannot place my cursor in the search field (top right of each forum page) to type a search. I can click the search button and then type in the "search term" field, but the search field at the top right always seems to be inactive.
The upper right search box DOES SEEM TO WORK WHEN I AM LOGGED IN to the forums, however.