From what I have heard and read both on the web and in news groups, the Apollo boards were very tempermental and there were many problems with them from a design standpoint that caused hardware issues for many people.
This is a CPU trap in which the CPU reports an error back to intuition, in this case, it's a blanket "illegal instruction" which could mean many different things, but, since that's an Apollo, I would make the assumption that there is a hardware issue. You might try reseating the device and any surface mount chips on the device and memory as well. Could be dirty pins causing erradic signals as well. I often clean pins (gently) and edge connectors with alcohol and a pencil eraser respectively.
I hope this helps you,
- Mike
