I have 3 WRT54Gs and one Ubiquity Bullet M2.  All were connected fine via RF on CH 1.  In an effort to minimize interference over a 20 mile path to another station, we decided on CH 3.  The bullet connected fine to the remote station on CH 3 (across the Las Vegas valley, I might add :) - still fine tuning though).

I changed the 3 WRT54Gs to CH 3; their physical locations remained unchanged.  Applied the change, used the "Save Changes" button and rebooted each of them.  They see each other, but not the bullet.  Oddly, I know I noticed that when I changed the first one to CH 3, it still saw the other two that I hadn't changed yet from CH 1.  At that point, I chalked it up to being tired / a fluke.

A WiFi scan from the bullet, and from at least one of the WRT54Gs, shows BroadbandHamnet-20-v3 on CH 1 (not CH 3!) (the bullet also shows a second entry - the remote station's -71 signal on CH 3).

I'm coming to the conclusion that for whatever reason, changing the channel on the WRT54Gs had no effect - is this a known issue?  

I know I can work around the 3 nodes being on RF only paths with the bullet; it was just my inability to replicate my original setup that was frustrating since everything worked fine on CH 1.