I'm having problems using both Hotmail and Twitter in Firefox (and Google Chrome) but they both seem to work fine in Internet Explorer. I can log-in to both sites but in Hotmail the drop-down menus and links don't work, and in Twitter the stream does not appear at all.

I've tried everything: deleted cache, history, cookies, disabled add-ons etc... I've also tried re-installing both new and older versions of Firefox and I've still had no joy. If anybody has any ideas for a fix I'd really appreciate it. I can't stand using IE but I am forced to at the moment.