If you go to Yongnam and fly or walk underwater around the SW corner, just dipping into the surrounding sims, all of a sudden the sim essentially freezes. Pings go from the normal ~100 msec to over 30000 msec and never recover till you quit SL. There also is a lot of disk activity, so I'm assuming that the texture cache is being flushed or something like that.
Anyway, I don't think that's correct behavior.
I reported it as a bug, but want to get some visibility to this, I'd hate for that to start spreading.