ath1 - athX are virtual interfaces(VAPs) created by Kismet(or any other application that can put the card in monitoring mode for that matter, i.e. airmon-ng). Every time you start Kismet, it will create a new virtual interface(athX) and place it in monitoring mode unless you specify an active one. It might be best to start the monitoring interface with airmon-ng and then specifying it when starting Kismet.
As for your stability issues, I would suggest that you update the MadWifi drivers that come with BT2 out of the box, there should be a module floating around somewhere. One other thing, BIOS level power management can interfere with Kismet(or any other wifi monitoring app for that matter), I would suggest disabling it for troubleshooting purposes...Code:airmon-ng start wifi0 kismet options here(I don't remember the syntax offhand) airmon-ng stop athX(where X is the interface in monitoring mode)