This issue could be a compatibility problem
Based on the information on the web site above, the motherboard requires an updated BIOS to use this processor. (Minimum BIOS 3878)
At this point you may need to test the motherboard out of the chassis, placed on a non-conductive surface like a newspaper, a magazine or something similar, and testing only with motherboard, power supply and processor and Heat Sink and fan. Make sure that all power cables are properly attached. Check if the system beeps. If the system still does not beep and the pro hot light is on again, you may need to swap the processor for another one or test the system with an older compatible processor (one that requires an older BIOS version to be installed)
We've encountered the exact same problem as well using the Intel DP55SB motherboard with the i5-760 processor. Intel's web site indicates that the processor and motherboard are compatible. We've followed Diego_Intel's suggestion to disconnect everything other than the CPU, CPU heat sink, and fan and to try running it outside the chassis. The problem persists. We can't try it with an older compatible processor as Diego_Intel suggests since we don't have one available. We've checked seating of the CPU repeatedly, and we are 99.9% sure both it and the heat sink/fan are seated properly. Is there any simple way to narrow down whether it's the processor or the motherboard that needs replacing?
Cool, I have exactly the same issue all of a sudden on my DP55KG board. Proc Hot light on. Replaced PSU for a new one, as system would no longer startup.
Then managed to get it going again after removing CMOS battery for >20 minutes. One time startup. As soon as I press power button to power off, the Proc Hot light comes on, game over. nothing works.Have to power off completely. Even then switching on the PSU after say 2 minutes, immediately Proc Hot comes on again. Board will never start again unless I do the CMOS battery trick again.
After such as CMOS reset, I removed the recovery jumper, and flashed the BIOS to the latest version (Nov 2010) via a USB stick, just as Intel explains in the recovery procedures. All of my effort in vain for a one time reboot only. As soon as I shutdown the OS or try to reset / power off with the soft power buttons the whole Proc Hot light fault starts again.
Cooling is not the issue, Have a big Arctic Freezing on it, but I even switched fans with the Intel stock cooler and it does not change anything.
I think the board is dead.
Went out to buy another one today, will try to find invoice to RMA the other one ...
After being ultra-satisfied (and still am using it) of my Intel 945GTP board (with a Pentium Dual Core 3,4Ghz) this one turns out to be a bit disapointing at present.
I prefer Intel reference boards over Asus and co, because I am truly convinced by experience that they run very very stable, but now I'm having second thoughts again.