It's very possible the dimm controllers are damaged from running while the dimms were not in all the way.
The CMOS is likely ruled out, as the problem now occurrs with the original RAM and you have done nothing more than physically change the RAM.
But if you want to go ahead and give the CMOS a try, you can probably reset it from within the BIOS, so you don't have to touch the motherboard. Go into your bios and look for "Reset to factory defaults", and that will give you the same results as the "Clear CMOS" jumper.
http://h20015.www2.hp.com/en/product...res93648&cc=us