Try using only 1 dimm at a time and keep using the same slot. if both fails try borrowing a friends dimm make sure it's working and install it, if you still get the same error messages at least it was your third try. After trying for three times make sure with a fourth try but make it a different brand, most of the time motherboards are very particular with the kind of ram you put in them. After doing all of the above and you still get the same error message, then you could conclude that it's a motherboard problem near the memory slot area.

 

Hope you do well with this minor troubleshooting task, happy computing....

I tried one DIMM earlier and the diagnostic utility will not run.  Will look around for compatible DIMM.

Good thing you mentioned that, when you start to see capacitors bulging its a sign to get a new motherboard or if you like and have the patience for it removing the busted capacitors and replacing them with new ones or from old motherboard just make sure they have the same capacity and values.

 

Happy Computing.....

  

One thing I just noticed is one of the capacitors on the motherboard next to the memory slots has a slight bulge.  I know this is a known problem with Optiplex GX270's.