Hi Deux Anges
What BIOS version do you have?
Could you please provide your exact memory model number?
Could you please provide your exact power supply model number?
What USB devices are you using?
i had the same problems too, check you have the latest bios, the latest driver for the network card, also check that your memory is installed corectly, in the first two slots close to the cpu.
Thanks for the replies. I've isolated the problem: RAM which is rated to 1.65V (They're OCZ Platinum 1333MHz, 2 x 2 Gb). Funny thing, I bought these specifically because they were supposed to be "low voltage" for my new i5 core, never thought it would cause problems with the motherboard. Nevertheless, switching off Enhanced Speedstep and C1 state as mentioned above seems to have "solved" the problem.
I have a good quality Ultra LSP 550 W PSU and only the keyboard and mouse as USB devices, none of these are likely to be the problem. I have the latest drivers for LAN, sound and Graphics. I have also downloaded the latest BIOS but have not installed it. From what I have read on the other threads and forums, this won't overcome this incompatibility.
I guess my only question at this stage is why the enabled Speedstep causes the reboots. Presumably if the voltage was too low it would be the case all the time and wouldn't start at all?
The ocz ram needs the voltage corrected in the bois. its at 1.5 volts and requires manual setting of 1.65. the acpi also had to be turned off. with those two things, the system was stable. (thanks Mr Brown).
using oc ram with powersaving options is rarely a good idea. using 1.5V "standard"-ram does not require disabling anything.