I had had the machine a year or so, and started getting some funky I/O errors. Seemingly random, they would cause the machine to crash at the most in-opportune times. I finally got frustrated enough after working through all my Mac owning friends and they were far and few between (We were all clueless about these) that I called Appel Tech support.
I described my issue to the support tech on the other end of the line. He listened patiently while I ran through my rant. When I fianlly wound down, he asked me if I was ready to try something a little un-orthodox.
I was somewhat taken aback by this, but so frustrated that I was indeed open to suggestion. He asked me if the monitor was sitting on top of the case (It was) and would I power the system down and set the monitor aside? I didn’t see what this had to do with anything as when I asked him if we were going to open the case he answered no. But I powered down and moved the monitor.
He: This is going to be a very low tech solution.
He: Please pick the case up about two and a half to three inches off the desk top. [I did this] OK now drop it! he said.
Me: Are you sure about this?
He: Yes sir, quite sure. So I dropped the case back to the desktop. He had me do it two or three more times. The he had me power it back up.
At this point I was kind of laughing, but the machine seemed to be humming along. We chatted for a minute or two and then rang off.
Turns out the expansion cards were spring loaded and dropping the unit to the desktop a time or two reseated the cards. I did this every 3 or 4 months after this call.
I never had another problem with the mac.