This is Debian bug #363523. Our users reports that swat segfaults each time he edits the configuration with swat. This appears to be reproducible with 3.0.21 and 3.0.22. I'll attach his smb.conf file
Created attachment 1866 [details] Configuration file for the user experiencing the problem
Fixed with r15465. Add a missing load_case_tables() and all is good with SWAT again.