4gig kit F2-6400CL5D-4GBPQ help!

[Flipeffect]

Ok so I bought this kit on newegg price was awsome but when I put both of them in and doesn't load up no video output everything is on but nothing on the screen?!.. and when I'm using just one of them it does load everything smooth no errors or lock ups but when I play games it lags every 7 second?!? and i tested my videocard(geforce 7950 gt) on another computer but it works just fine!. Ahh please help!

Could it be my motherboard? using a

ASUS M2N-MX SE Plus AM2+/AM2 NVIDIA GeForce 6100 Micro ATX AMD Motherboard