[Moved to Netscape, Firefox, Mozilla, Seamonkey Forum by profman. Do not repost. 6/21/2008]
It turns out that the easiest solution is to make a new profile by starting thunderbird with the -ProfileManager option (this is described in an article in the mozilla stuff and can be found by google 'mozilla profiles'. The profiles are similar although Thunderbird keeps its profiles separately. (In windows it is /windows/application data/thunderbird/ Once the new profile is found to be working, either continue to use it, or copy the whole thing to the original default profile. (really uneccessary)
The problem occurred when the existing profile became corrupted, and JS3250.dll couldnt handle it. I did it by setting up an extension 'quicknotes' and got into trouble.
Backing up the profile elsewhere is a good idea as it is simple to restore a working profile. hope this helps.