Aurora r3 intermittent lag

Hello! I just bought an aurora r3 desktop with an i7 processor and 6gb of RAM. I also have the Nvidia GeForce GT 545 graphics card in it. The desktop was working fine for about 2 and a half weeks and then i started to experience some lag. My mouse would just lag across the screen for about 5-10 seconds and then it would go back to normal. I also record my xbox with an happuage HD PVR. When the lag occurs my "capture module" (which records the game play) will freeze and the part of that recording (when the lag occurs) will get cut out. It is happening very frequently and I'm thinking it is a graphics card issue because my graphics card has failed three times so far. It will go unresponsive and come back 30 seconds later. I haven't seen a fix for this problem anywhere so please help!