Beep no beep

Hello,
i have a such a problem which leads me to think that its a RAM problem, i get no display, no motherboard and mouse, everything in the cabinet works fine.
When i remove the RAM, it gives me the normal 3 beep, NOW sometimes when i insert the RAM STILL i get the 3 beeps and when i just shake the RAM in its place, then no beep but still no display,
also sometimes the intel motherboard which i have boots up and gets hanged on a two digit alpa-number 5A.
i have one 500GB sata, DVD sata and 2 IDE drives with integrated video.
I have four slots for RAM and i have tried in all the 4 slots,
planing to buy a new RAM, but not sure if RAM or the MOTHERBOARD is the problem?
any help would be highly appreciated.