Its hard to say for sure but, if you have swapped out RAM and tried multiple different ram sticks in that configuration. Made sure that you have tested both RAM slots with a known working stick then it looks like it could be the motherboard but, did you make sure your motherboard had only the absolute necessities connected to it while running your tests? Maybe even try another power supply if you can to see if power might be an issue. (I highly doubt it is but, I personally try not to make assumptions when troubleshooting) Plus if it works then you don't need to buy another motherboard. It really depends what you have more of though. Time or money. Which warranty ended? The manufacturers warranty? Or the warranty provided by the store? Maybe test those sticks of RAM with the latest version of Memtest86. I've had sticks of ram post just fine only to find them get 20000 errors within seconds on memtest86.