Links don’t work in Outlook (XP Pro, Outlook 2003, Firefox, IE8)

I recently started using Outlook 2003 and I’m pretty happy with it except that when I get email with embedded links they don’t work. When I click on them nothing happens. But if I look in the HTML and extract the href and paste it into my browser they go right to the site (i.e. the links are valid)

My default browser is Firefox, and before someone says, “Outlook only works with IE”, please note: Oulook’s Help is also HTML with links and when I click on them they come up just fine – in Firefox!. So this problem only seems to apply to email messages.

Thanks in advance!

PS – I do have IE8 installed because I develop websites and I need it for testing, but I don’t want it to be my default browser.