Windows Messenger Error

Hi, I downloaded the new version of messenger, and installed. Then the next day, every time I try to open it, it opens in the system tray, and then comes up with an error whilst trying to open the program to talk to contacts. It says: ['Traceback (most recent call last):\n', ' File "c:\\pyagcore\\pyagcore/_init_.py", line 3 , in <module>\n',, 'ImportError: No module named shell\n'] Can anyone help? IE7 also has the same problem, but firefox and chrome do not.