Random freezes and boot issues

Hello people. Been having a lot of freezes recently, hope somebody can help.

System:
Windows 7 Ultimate 64
Gigabyte H67M-D2
i7-2600 @ 3.4GHz
8 Gigs of ram
GTX 460
Corsair TX750w
WD Green Power

When these freezes happen the system locks up and the sound usually starts looping, sometimes changing a bit depending on mouse movement. I can still move the cursor around. Only thing to do is a reboot.

When I turn the computer back on there often is no image on the display, even if I disabled the power completely from the PC before starting it up again.

There are two ways I found to get an image back on the screen:
1: Let it boot into windows (Windows sometimes loads up correctly it seems, as indicated by normal sounds), then restart the computer again. Second boot will have an image on the screen.
2: Removing the RAM and inserting them again.

The freeze seems to happen at random, sometimes when in a game, sometimes when browsing. Sometimes not for days, sometimes several times in a row.

There are no BSODs, so I have no dump files to share. Event viewer sometimes shows "Display driver nvlddmkm stopped responding and has successfully recovered."

I tried various stress testing programs; prime95, FurMark, some WD harddisk check etc. but nothing really seems to set it off.

I also tested the RAM individually as well as the sockets with memtest and it came out clean. The system also freezes running with only one block of RAM.

Any ideas?

/Sancia