I did a search on that reg entry. Apparently here's how it's supposed to work.
Setting Maintainserverlist to TRUE forces the PC to act as a master browser if no other PC is acting as such.
Setting the same to TRUE if another PC is acting as a master server list puts that PC into a backup "mode" when it sees a master on the network.
Setting Maintainserverlist to AUTO causes the PC to take over the role of a master if no other master exists or acts as a backup if not enough backups exist on the network.
Setting it to FALSE forces the PC to never hold a master or backup role even if no master browser exists on the network.
In other words, putting all the PC's on a network to TRUE causes one PC to become the master and the rest to become backups. Expected behavior for that setting. That's why it works for you when you set them all to TRUE.
So it appears there's a deficiency in how Maintainserverlist set to AUTO works. I'm going to have to try this when I get home tonight.
In any case, a quick peek through the MSDN and Technet pages, Microsoft is rather vague on how it all works. MSDN has better information on a technical basis, but hardly any nutshell information. Oddly enough, I did note that the browser list is supposed to be one master and one backup for a network with 32 or fewer PC's and an additional backup for every 32 beyond that. Seems to me that the AUTO setting can't decide which PC should act as a master and backup.
Here's a thought. Anyone with problems using non-Windows PCs in their network? Linux, Wii, PS3 perhaps? Anyone that don't have problems, are they using a pure Windows network? Just a thought, I recall my Barricade refused to list any Linux PC unless I used some hacked firmware.
Corrected annoying spelling error