Hi John,
I've used ASA 5 DB for years with a ASA 6 so not sure what the problems is? However ASA 6.0 -> 6.2 was quite buggy to say the least. What problems are you having?
However, the easiest way to "upgrade" an DB is to unload the ASA 5 one and reload it in ASA 6. You can do all this vis Sybase Central.