Some more information, I appear to be running several large sites now, stable. I had to increase apc.shm_size, roughly 256MB per wordpress site (these are very busy, very content heavy sites)
With memory allocated lower, i was crashing with the above messages, had to wipe the files listed above to get the site functioning again. Increasing the shm size (now at 768) and all appears stable.
I'm also now running mod_ruid2, DSO, and APC.