Either you have (Multiple or) a single dead RAM stick, or memory slots.
How many sticks of RAM are you using? Also, run each stick on Mem test and you'll find out what the problem is. If the sticks are fine, it's a dead Slot. I would know because the motherboard I use now came with 2 dead slots! I thought it was a CPU issue the whole time ;'( don't make the same mistake! lol