Broow,
Sniffer Pro can detect Microsoft network services. PRINT, SQL, TIME, xDC, BDC, PDC, WINS, or RAS from Browser Announcement Frames. This is where Sniffer's expert alarm will track and alert when this the announcement frames are seen. I would suggest to check the event viewer of the PDC in question, see if other servers took over elections, etc. on the NOS side. Here you should find some answers...