I ran into a strange problem just the other day. Outlook all of a sudden stopped opening *.eml attachments, which included a lot of these "cute" forwards people often send. The message just showed up blank. After going through a million different things including checking file associations, I found that the problem was the Google Desktop add-inn for Outlook. Once I removed Google Desktop all worked fine. Another option for this is just to disable the add-inn in Outlook. In Outlook 2007 you can find the Add-inns by following these steps.
1. Open Outlook
2. Click Tools
3. Click Trust Center
4. Click the Add-inn you want to disable, in this case the Google Desktop add-inn
5. At the bottom under manage, click Disable Item
6. Click OK, then close and reopen Outlook
