NZXT 2 x 120mm fan trouble

Hello, I was wondering if someone can help me. After watching razetheword video about Asus fan xpert 2 I realise that one of my side fans aren't spinning. I have the asus v formual motherboard. I know the fans used to work because after I opened up my system to install a DVD drive I kept unplugging one of the fans from the motherboard by accedent. But now after a close look at the side with my phones light i can see that the blades aren't spinning. I opened up the side to check that its plugged into the motherboard and it is. I even tried swapping both side fans on the motherboard to see if its the actual fan but it wasn't because the one that stopped spinning now spins. Could i have someone wrecked one of the fan headers? The pins aren't bent or anything.

Maybe a bios setting i changed by mistake?

 

Thanks heaps for your help

 

Ian 

oh update. When the pc boots up all the fans are working. But when windows has finnshed loading, thats when one of the 120mm fans stops spinning

try re-installing fan xpert and/or check and edit your fan speed graphs for that fan.