Windows Live Mail will receive new mail but will not open any.

The Windows Live Mail i have been using for years with three email accounts from different domains has developed any issue opening any mail. The program will open, receive all incoming mail, but when you click on any mail in the list it will not open & gets message "A problem occured while trying to open this message". The problem started after i paid Microsoft for a Windows Upgrade from Windows 7 Home to Windows 7 Professional. I have spent hours on the phone with Microsoft support speaking with clueless people, and the outcome is they won't really help me because they say it is a Windows Live Mail issue and they don't support free services. The fact that the upgrade I paid for caused the problem means nothing to them. I have tried a program repair, and I have tried to unistall & reinstall the program. Looking for any helpful advice from the community. Thank you!