Okay, I don't believe this is an error or bug, seems to be rooted in the way information flows between the sims. But I've heard a few folks in the Welcome Area who thought they were having problems when parts of the Welcome Area vanished.
Basically, if you stand on one of the walkways around the fountain, then position your camera somewhere in the sim catty-corner (straight across the fountain) to yours, and wait 1-minute... the three sims around your av's current sim will vanish, including the sim with your camera. Once you reset the camera, the other sims reappear.
It's an interesting effect. I repeated this several times, positioning the camera in the opposite sim looking back towards my av. After a minute, all evidence of the other three sims would vanish, including avs. Interestingly though, if an av walked from my sim into one of the vanished sims, the av would remain visable.
