Rated 5 out of 5 stars

Never mind, it suddenly started working in T-bird again... might have been a problem with another extension.

This review is for a previous version of the add-on (1.3.20110715).  This user has a previous review of this add-on.

Cool, thanks for the update.
I got around to trying it with Thunderbird 5 (both Linux & Windows) and had no problems, so I was confused by your initial report.
Glad it's resolved itself!