Got a notification today to upgrade to the latest version of Thunderbird 1.5.0.7. The update downloaded and then crashed while installing on the next launch. Now when I try to launch Portable Thunderbird the process runs for about 5-10 seconds and then just disappears, no error messages or anything. Renaming my thunderbird profile and trying to launch did not make any difference either.
You have to launch TBP again after the update process finishes. If it constantly runs the update process, you have to redownload TBP and replace the \App\ folder. Then autoupdate again.
Vintage!
That may be a failed update. It's a bit more likely on a flash drive, unfortunately, than a hard drives (slower, a bit less reliable concerning connections to the PC, more likely to run out of space, etc).
You can try grabbing the 1.5.0.7 pre-release of Thunderbird Portable and installing it right over your 1.5.0.5 install. None of your data will be affected (and, hopefully it wasn't corrupted by the failed update). You can find it in the beta forum.
Sometimes, the impossible can become possible, if you're awesome!