Unable to wake up the PC

I have Intel DG35EC motherboard and Intel Q8400 cpu. Earlier I was using AMD Athlon X2 6000+ with Asus M2N MX SE Plus Board and I was able to wake up the computer from hibernation on alarm. Now since the new intel board does not wake up from hibernation. It can wake up from S1 ie if PC was shut down. But it does fail to boot properly very frequently may be 3 out of 5 times. The power button is on but no HDD activity no display on screen. I have also observed that it can not wake up if monitor was off.
I have updated BIOS & also checked power connections. I have tested it with various OS like Ubuntu, Fedora, Vista. What could be the problem? Please Help. Thank you in advance.