ZDTips, Compiled by Eric Halingstad: "Master Browser election problems
A common problem that tends to creep up in Windows NT involves Master Browser elections. The main symptom of this problem is that you'll find numerous entries in the Event Viewer of your Primary Domain Controller (PDC). These are generally 8003 errors that will occur every 12 minutes. In most cases, these are caused by one of two things. The first is a computer on the same subnet that has an incorrect subnet mask. If you correct the mask on the computer, usually the problem will go away. The other thing that can cause this problem is having a router that's forwarding UDP broadcasts. If you configure the router to stop forwarding these broadcasts, the problem should go away. "