A collegue and I just found out that the FTP fuction listFiles() has a problem exactly today on Feb . 29th as we have leap year.
We just guest this, but as we have found this blog entry we were pretty confident.
http://blogs.lodgon.com/johan/Leap_year_issues_in_apache_commonsnet
Unfortunatelly also still an unassigned issue for the guys
https://issues.apache.org/jira/browse/NET-188
If you have strange problems today with tools that rely on this framework you should have some more coffee and wait for tomorrow 
Christoph