Memory Module Failure detected. Lights 3 & 4 come on the XPS Dimension 210

Same problem with 2 optiplex 3010 , 3 months after i bought.only lights 3 and 4 solid amber.

I exchanged dhe Ram module , let only the motherboard and the proccesor (and tested Ram modeule) , but nothing shown on screen, the same symptom.

Which may be the couse of this failure , because these computers were protected with ups?

I have bought  many of these models but only these 2 have this problem.

i would appreciate any idea of solving this ( exchept changing the motherboard :emotion-5:)

Klajdi