Rated 5 out of 5 stars

Got it.
Tracked it down to FastestFox add-on.
Uninstalled it and FireFTP works just fine.

This review is for a previous version of the add-on (1.99.2.1-signed).  This user has 2 previous reviews of this add-on.

I'm currently talking with the author of FasterFox to find a solution - seems to be a problem on their end...