I have the same problem as the "nobodies" above.
The GUI freezes occasionally when I start the compare or sync process. A popup window is showed and then you can do nothing more. No log.txt is produced!
I'm working on a Kubuntu 9.04 machine, but I had the same problem on Kubuntu 8.10. I'm syncing an autofs folder with a samba folder with about 30 GB data in a lot of files and subfolders.
2009-05-01 01:27:47 UTC in JFileSync - Java File Synchronization