In the "Edit File Set"
In the window "Files and directories to skip"
If you have two lines of directories to skip and decide to remove them all it corrupt the bacula-dir.conf file by at best removing some file sets, at worst making the file unusable.
If you remove one by one the line to skip (remove the line / save / come back / remove the line / save/ etc...) it works fine.
I forgot
Bacula 2.4.4-1
Webmin 1.48
Debian 5
Would it be possible for you to attach your original bacula-dir.conf file to this bug report? Or least the section that got corrupted..
File before corruption (I removed the passwords)