P5E Deluxe POST issues

Hello people,

I'm here seeking help. I'm pretty sure I have a defective MoBo, but since things are very strange, I'd like to know if anyone has this same board and if they had the same issue. I've assembled (actually, the guy I bought it from assembled it, but I witnessed the assembly and I already disassembled everything but the MoBo/CPU pair) the following system:

- Asus P5E Deluxe Motherboard (rev 2.00)
- Intel Q9550
- 2x Kingston 2GB RAM - no dissipator
- ATI HD 4870 512 MB (Sapphire)
- 550W Seventeam PSU
- Snowfall Cooler from "Empire" (unknown brand, but seems like a good one)
- DVD Recorder
- Samsung 320G HD

On first boot, I've installed Windows 7, some drivers, etc. I never touched the BIOS -- rev 302 is currently installed --, which means that all OC features where on AUTO setting.

Then I began to experience a chain of problems:

1) The Keyboard (a very simple PS/2 model) would simply stop responding. This means that:
a) No key that I pressed would do anything -- even caps lock wouldn't affect the LED
b) The last key pressed, if any, would keep it's stated, so if I was pressing "W" (foward) in some game, the character would keep going in that direction.
c) The scroll lock LED turned on.
2) After a simple reboot -- software or hardware -- the computer would refuse to POST:
a) There would be no BEEPs from the MoBo, but keep in mind that I have no case speaker so I'm relying on the sound card to transmit some sound.
b) There would be no video at all
c) All fans (CPU, video and PSU) would spin correctly for as much time as needed.
d) The HDD led on the Case would not blink.
3) When this first happened, I suspected a short or something on the component's, so I opened the case and reconnected some cables and pressed some stuff. This solved the problem, but only on the first or second attempts. After it happened for the third time, nothing could resurrect the PC.
4) I took the computer back to the retailer. He disassembled it, part by part, and nothing. I *think* that when he finally removed the MoBo from the case, it began working, but I was distracted. I don't know if he removed the MoBo and did something else OR if the computer already responded before he removed it. Since he could not zero in on the error and the MoBo worked for at least one hour after he reassembled it, he returned it to me, saying that it could have been some bad seated memory or something. Of course, I didn't though so, but I decided to give it another shot, after all, he tested it for quite some time. I took the PC back home.
5) Since I was suspicious that the keyboard was causing the failure, I tested it with another one. I could use the computer for quite some time then, at least 1h30. I installed a game, played it for a while and everything looked fine. When I was almost convinced that the problem was with the old keyboard, it froze again. I must stress this: the computer kept going fine. Everything was working as far as I could tell: mouse, video, sound, HD and probably CD/DVD. But since I had no input, I booted it (hard boot, since I had no keyboard and was inside a game). The computer would again not respond.

If someone could help me figure out what is wrong, please post anything. Some questions come to mind:

- Would I get sound from the MoBo without case speaker? Keep in mind that this MoBo uses an offboard soundcard.
- I've actually seems a number of posts (in tomshardware and other places) about this board having many issues. One even pointed out that beneath some sticker there is a Rampage Formula logo, but I've not found that. But some of them tells about PS/2 problems with this board and says that I should use a USB keyboard instead. Well, I'm not very fond of the idea that, since the MoBo has a problem, I should exchange my keyboard, but I would do that if I was confortable with the board -- which means that, if the board always had problems with a PS/2 connector but came back into action once I disconnected it, then I would risk doing so. But what if there's something shorting inside de board and it happens even without the PS/2 connector on?

Well, sorry for the long text, but I thought it'd be better if I gave my complete analisys on the subject.

Thanks,
Storm aka Bruno