I've got the same thing happening and I don't even have an 845PE board!! It's an ECS board with the crappiest VIA chipset ever, but that's another thread. I used this board for about 5 months with an antec 300w ps with no problems. Then I start getting these cold boot problems, so I get an antec true 430, and the problem persists.
If I hold the power button on the case for a couple seconds the first time, it helps, but if it doesn't work, it usually will the second time. After shutting down, and then turning it back on, it takes like 15 tries. I have to wait for an hour to get it to turn back on.
Just bought an albatron px845pe pro2, so hopefully this will solve the problem (fingers crossed, knock on wood, rub rabbit's foot

)