I get a "test message" when Private Messaging is enabled

Team WPMU,

OK, I've got a tough one for you that I've been wrestling with for a while. When I activate Private Messaging in BuddyPress, any non-member sees a "Test Message" when they visit the network -- on every page they visit. I've disabled PM, and have since the beginning of the site to prevent disturbing the visiting public, but I would like to get it working again.

I maintain a mirror site, thedigitalcomic.om, as a test bed -- nearly identical to this site in every regard just on a different server -- and it does not have this test message issue. It is only on this install -- which happens to be the live site -- where things are awry.

Any ideas or help would be greatly appreciated.