Strange problem with 955 pro

Installed MoBo and processor and 2X1GB ram sticks, everything OK,
Started loading programs, everything OK, then rebooted overnight and system
would not even Post, on screen it hung after identifying processor, right
where it should say Memory interleaved, it just says Mem, and then stops, I
left it alone for a while and eventually it completed boot and everything
was OK, so Now I have a system, that takes about 25 Mins to complete boot
up, always hangs after identifying CPU,
Is my memory bad??, I have two sticks of 1GB DDRII Apacer Ram (PC4300).
As long as I leave it alone the system eventually boots and works fine,

Freddie