pc blocks time to time

Hi!I'm having a little problem lately,time to time my pc would block,i.e,no response when i move the mouse nor when i press any key.I don't know what's wrong.Can it be because i've added two additional sticks of ram or is it just pure coincidence because i never got this problem before adding any more ram on my pc.It's already almost two weeks since i've put another two compatible sticks of 256MB DDR333(because i already had two on my pc before,same DDR333)and i did not notice any problem since i put them,but it's only two or three days to now that my pc is blocking time to time and everytime it happens i need to push the reboot button.

Can anyone confirm me if it's a memory issue or not?

Thanks.

Edit:I just performed a test using Microsoft Windows memory Diagnostics and succeeded in every pass(i've ran two passes in total though only one was enough,but just to really make sure that nothing is wrong with my memory).

So where can the problem come from?Any idea?


Vincent.