Thunderbird version (20090812)

I've been running TB off a USB stick via ThunderbirdPortable.exe for
sometime with not problems, however recently it's started being very
slow. I've done the normal stuff like compacting folders and even
drag'd the drive but problem still persists.

Looking on the Error Console there a quiet a few errors pointing
various .js files.

How can I work out which add-on's these refer to so I can reinstall ?