Freezing after reboot

[nemtaro]

Hi there,

After working fine for about a year, my system is now freezing when restarted from windows (or ubuntu)

The OS would shutdown, and it seems to restart as it normally did, but the motherboard beep never comes back, the hdd light stays on, and nothing happens until I force it to shutdown.

Is this a PSU problem? What else could cause this?
Any suggestions or idea would be appreciated!

Here're the system specs:

 

[icantflybfplane]

depends what psu you have. I've heard certain psu dont work well with that motherboard i cant think of the psu that is incompatible with it ill try and look it up in the mean time

 

[nemtaro]

thank you,

the PSU is a Diablo 550W ATX, connected to the motherboard through a 24-to-20 pin motherboard power connector.

here is the PSU:
http://www.tigerdirect.ca/applications/searchtools/item-Details.asp?EdpNo=541436&sku=D15-1000

This is probably PSU related, right?
Would you suggest a decent, compatible 600W PSU for this system?