There is a critical bug in the January 27, 2012 build of Thunderbird Earlybird (11.0a2) which is preventing the application from launching on Windows. This is believed to be the result of the check in of Bug 701371 – Rename mozutils to mozglue, and move it to top-level. A patch has been created and uploaded for the next build. Users who have already updated to the broken build will get the message below along with a Windows ‘Program Stopped Working/Responding’ message. You will need to manually reinstall Earlybird by downloading Earlybird from the Thunderbird Builds page. We will post an update when this issue has been resolved.