I'd head to a Thunderbird forum next.

by R. Proffitt Moderator - 9/2/12 6:50 AM

In Reply to: Mozilla T'bird by Art Keetra

They discuss that software and if it's a bug they usually enter it for a fix.

Importing can be limited but did you try the old TWO STEP? That is, did you export it from Live before trying to import it?

Since this is widely discussed I'll stop here.
Bob