Rated 5 out of 5 stars

Very useful program... until now. It has just started to transfer files as blank. For instance a 2KB web page will transfer as 0KB. Same page transferred to same host with filezilla or cuteftp transfers as 2KB. Version 2.0.7 and FF 16.0.1

This review is for a previous version of the add-on (2.0.7). 

Hm, not sure what could be the cause of the issue in your particular case - perhaps some firewall software? If it works in Filezilla perhaps try Reseting Firefox: http://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-most-problems