Might also be a thermal problem as your A2000 always does well for some time, and regularly fails after some time. Especially flicker fixers / scan doublers get unexpectedly hot. I have an external flicker fixer for my A500 and once nearly burned my fingers on it. I think I'll provide it with a fan before using it next time... it was too expensive to just burn it. No idea why the manufacturer didn't think of that.
Or, the PSU might be overloaded with all the hardware you have. If it is not a heat problem, try to run the machine with less expansion boards and see whether it is stable then. I'd first remove the 386 board, then check stability, if it still fails, remove the flicker fixer and try again. If you can, exchange the PSU with one from another A2000.
