I was monitoring memory when the system hung and it didn't appear to run out of memory. I've been able to do some more testing and it appears the problem is really just my crappy DWL-G520 card. I've now seen some hangs in all modes so I'm now trying to hunt down another PCI wireless card that is supported. That's not easy as it appears most manufacturers have moved to a newer set of chips that aren't supported in NetBSD drivers (yet). Between wikidevi.com and Google I've been able to locate some potential candidates that might be available locally though.
So sorry for the false alarm on hostapd. The problem appears to be in the ath driver with the A3 firmware in the DWL-G520. Or it may just be really crappy firmware in the card itself.
