There's a longer discussion but it's not found so here's the short version.
1. Set your browser back to Internet Explorer.
2. Google DOUG KNOX HTM HTML ASSOCIATION FIX.
3. Apply that fix (as before, it's good for XP, Vista and 7.)
4. Reboot and retest.
Get this pop up error message when I try to open links in Outlook 2010:
General failure. The URL was: "http://app.bronto.com/public/?q=preview_message&fn=Link&t=1&...", Class not registered