I had a similar issue on a fully refurbished A4000. In my case it turned out it was one of the memory sticks had was duff. I suggest removing them all, dusting it with compressed air (there are other suggestions online for improving contact but I forget) and reseating them one by one, until you isolate the faulty one.
I assume you have tried removing and/or reseating any other expansions (including the PIV). Try also another processor card if you have one handy. Don't loose your cool, chances are if you have no visible battery/capacitor damage then it's something straightforward to resolve.
