Solution for Vista:
1. Close Outlook.
2. Go to "Programs and Features"
3. "View Installed Updates"
4. Find "Security Update for Microsoft Office Outlook 2007 (KB2412171)" that you might have installed on 2010-12-14 or 2010-12-15.
5. Double-click on it, it will uninstall the update.
6. Restart Outlook.
Keywords: Windows, 2412171, KB2412171, gmail, POP3, mail, e-mail, email, account, fails, error, troubleshoot, solution, help me.
P.S. I hope Microsoft already knows about the problem, or is it "by design" and you need to change some new setting to make it work?