Rated 4 out of 5 stars

yazan: Blackie tarih: Ağu. 21, 2011 ·

FireFTP on Firefox 6.0
I too experienced "Alas! problem.
Download of add-on
FireFTP button
was my solution.
Hope this helps

This review is for a previous version of the add-on (1.99.5.1-signed). 

yazan: Mime Čuvalo (Geliştirici) tarih: Ağu. 22, 2011 ·

There's been some reorganization in the new Firefox. The new FireFTP button is listed under Tools->Web Developer. Alternatively, you can also add it to the toolbar by customizing - see also: http://support.mozilla.com/en-US/kb/how-do-i-customize-toolbars