Outlook 2003, SP 1, WinXP

I've been using Outlook for a couple years with very few problems, but a
couple months ago it started locking up whenever I clicked on a link in an
email to open my default browser, IE6, SP2. This happens approximately 75%
of the time.

After I ctrl-alt-del to shutdown Outlook, it will usually work on the first
link, after I restart Outlook, but will again lockup when I try it a second
or third time.

Anybody know what's going on?