Motherboard issues

Hello,

Due to some compatibility issues between the memory ram and my former mobo (MSI P45 Neo2), i decided to buy new memory rams (Corsair XMS2 ). The problem was that, after i booted into Windows and tried to play some games, the BSOD appeared. I tried memtest and i found out that there are some problems with my memory. So, I bought the Corsair, but the problem remained. I thought that the mobo was the problem (MSI P45 Neo2) and I bought a new one (Asus P5Q Deluxe). I installed it and I started the PC. After a few seconds I smelled something weird, like some burned plastic. I've restarted the PC, thinking that smell was from the thermal paste, but it continued to smell, until the PC shutted down. I tried to start it again, but when I do that, the cpu's fan starts to spin (for a millisecond) and stops, the video card's led turns on and off very fast. If I remove the 8-pin cable, the cpu's fan spins normally, so does the videocard's led and fan, but I don't get any image on my monitor.

I changed back all my components to my former motherboard (MSI P45 Neo2) and the PC started normally. I said that I'm going to use this mobo until I find out what's the problem with the new one (Asus P5Q Deluxe). But, after connecting all the components, my PC was behaving in the same way. I removed all the unnecessary components, leaving only the cpu, video card and mobo, but it does the same.

The CPU is a Intel core 2 Quad Q9550 @ 2.8 GHz
The PSU is a X-Power @ 700W
The video card is a Sapphire Ati radeon hd 4890

If you need other details, please let me know.

Thank you very much.

bump

I tested it with another PSU...same result. I'm pretty sure that the GPU is ok. The question remains: which one is broken, the motherboard or the CPU?