My .02 cents... I hate building a "house of cards" on a shaky foundation. Get that '030 replaced and see what other issues the motherboard may have before pointing fingers at one component or another. Try rebuilding the system piece-by-piece, from the ground up, and see when the issue occurs.
Of course, if you can just swap in another CPU or processor card and the issue disappears, then you're golden.
Also, here's a link to that Amiga911 disk Paul mentioned, earlier:
http://amiga911maker.site11.com/index-1280.htm Might have something helpful on it?
