After upgrading jEdit to 4.3pre6 (with FTP plugin 0.8) I was no longer able to browse listings on one particular FTP server. The behavior persisted through 4.3pre7 and pre8, so I decided to troubleshoot the problem.
The FTP server is IIS 6. What fixed the problem was configuring IIS to use Unix directory listing style instead of MSDOS.
I used to be able to connect to this server without incident using previous versions of jEdit.