Pc will boot with 1 slot of ram not 2

[joshisfear]

when i bought the pc it had both of the ram working but i removed the ram and tried putting it back down and now my pc will not boot just gives me a beep code 4 long beeps my motherboard is gigabyte ( the long beeps mean something is wrong with my ram ) i have had this ram working before but now it only works with 1 in the ram slots not both it boots up fine if i just put one of them in Slot one but if i add the other one into slot 2 pc says nope and gives me the Post Beeps

what i have tried

i have tried re seating the ram multiple times
switching ram over different slots 1 and 2

is this a case of pulling my cmos battery out for 10 seconds or something not sure please any advice would be nice

win 7 64
gtx 570
phenom 955 x4
corsair TX 650 watt

 

[karl_ranseier]

check if one of the ram sticks are broken. put 1 stick in and run memtest. if there are no errors replace the stick with the other one and run memtest again.

 

[kajabla]

Yep. Check both in a working slot, then check one stick that you know to be working in the slot that may not be working.

 

[jitpublisher]

Check the RAM voltage in the BIOS, make sure it is correct for your memory. When you pulled the memory and reinserted, it might have changed the voltage setting to something lower than required to get both sticks working, especially if the sticks require voltage that is a little higher than the default setting. Even if the default setting is correct, you may need to raise it slightly to make both sticks work properly.