Ok, well next thing to try would be:
1. Save your preferences:
- navigate to Plus > Preferences
- at bottom left click import/export
- choose Export current settings
- follow the wizard to save them to a file (.pld)
Optional: If you have custom sounds you can save those too by going to Plus > Sound Library..Import/Export at bottom left, choose export and follow wizard.
2. Uninstall Plus! again, this time remove everything (preferences too) and reboot.
3. Go to
http://www.msgpluslive.net/download/ and download a fresh copy of Messenger Plus! and reinstall from that file (save to computer then run it).
Now sign in again and see if the event viewer will open.