Thanks for all the help. So, I have been running Donpachi at 336, default settings, no tinkering. The game always crashes at some point, it's different every time. Today I had it crash at the ship select screen, at the first boss entering, and on the title screen. It's different everytime. Same thing with MAME4ALL.
It's so frustrating beause slaneesh has put together some absolutely amazing emulators, and I know everyone is enjoying these.
I wonder, would I benefit from getting a new zImage? I'm using the unofficial one with the shut-down option built in. I think I'll try going back to an old one.
Anyway, thanks again for all the help!