Failing to start program after update

"thunderbird.exe has encountered a problem and needs to close. We are sorry for the inconvenience."

The error message appears, without the program even appearing first. It's happened every time since I updated to the new version number of thunderbird (minor update, e.g 2.10 to 2.11 or whatever number it is now).

Has anyone got any ideas on maybe how I could fix this, or if not where can I find backdated versions of thunderbird portable?