System hangs on shutdown every other startup

[CottonRabbit]

I recently decided to upgrade a computer a bit with a new mobo (had an ECS mobo) and Vista Ultimate 32bit.

Foxconn P9657AB
C2D E4500
2gb OCZ DDR2 800
MSI 8800GTS 640
320 gb Maxtor SATA HDD
500w Antec Earthwatts

At first, it wouldn't post unless I reset the CMOS every time, which I fixed by updating the BIOS.

Now the system hangs on every other shutdown/restart, always. The screen goes blank, my USB devices turn off, but the hard drive often keeps clicking for a few more seconds, and the fans keep spinning indefinately. If I reset, the computer shuts down fine once, and then it hangs the second time it's shutdown. I also noticed that my PS2 keyboard stops working after logging into Vista as a prelude to a frozen shutdown.

Anyone have any idea what is going on?

 

[LOUISSSSS]

HMM psu?? pull it out for 10 mins and reset the CMOS (just to eliminate any bios problems)

make sure ur not OC'd and ur CPU is getting enoguh voltage (a few notches above the VID)

 

[dr4gon]

There's no way it can be the PSU. Make sure your RAM is running at the rated 2.1V by adding +.3V to the vram (base is about 1.8V which is definitely not enough). Then try setting higher ram timings and setting the ram speed to either 533mhz or 667 mhz.