I use Outlook 2003 and FireFox 1.5 at work all the time without any trouble--do you have the latest Office service packs and other updates from Microsoft? Check out
http://update.microsoft.com/ if you're unsure.
If you're running Outlook Express instead of Outlook 2003, save yourself some trouble and just get Thunderbird from
www.mozilla.com; it's the perfect complement to FireFox
