I've bought some new memory for my P5B. It's the same memory as I already have in, Geil PC6400 ultra. I already had two sticks configured as dual channel that worked no problem, one in the Channel A yellow slot the other in channel B yellow slot. So they were configured as dual channel. Installed the other two sticks and the computer would not post. Took out the two new sticks and it still will not post. For some reason only channel B memory slots now work. I've tried all different combinations and nothing. As soon as I put anything in A it will not post. Any ideas? Is it new Mobo time? I have the latest bios. I've searched the web and found other people with the same problem but no solution.