If you see this in either your /var/log/samba/log.nmbd or /var/log/samba/log.nmb file: (time, date, names and IP numbers will be different)
[2001/11/23 04:02:01, 0] nmbd/nmbd.c:sig_hup(92)
Got SIGHUP dumping debug info.
[2001/11/23 04:02:01, 0] nmbd/nmbd_workgroupdb.c:dump_workgroups(292)
dump_workgroups()
dump workgroup on subnet 192.168.1.2: netmask= 255.255.255.0:
CADD2(1) current master browser = LIMELIGHT
LIMELIGHT 400c9b0b (March Networks SME Server)
[2001/11/23 04:02:01, 0] nmbd/nmbd_workgroupdb.c:dump_workgroups(292)
dump_workgroups()
dump workgroup on subnet UNICAST_SUBNET: netmask= 192.168.1.2:
CADD2(1) current master browser = UNKNOWN
LIMELIGHT 40099b0b (March Networks SME Server)
[2001/11/23 04:03:04, 0] nmbd/nmbd.c:sig_term(65)
Got SIGTERM: going down...
The problem is Samba (I think). I have the same problem on two servers. Some event triggers samba to dump the workgroup and loose the primary server status. My only fix was to change the 'os level = 165' and set a cron four mins. after the dump that did a samba restart. Hope you do not have the same problem. No one had any real fix for mine.