Faulty PSU?

Hello, I have assembled some parts together to build a new PC. I never thought I would bump into a problem regarding my GPU + PSU combination. Before I continue here is the parts that are probably needed.
PSU: Thermaltake Toughpower Grand 850W (TPG-850M)
MoBo: Asus p9x79 deluxe
GPU: MSI GTX 660 Ti Power Edition IV Twin Frozr

The problem is that when combined (psu + gpu) the motherboard fails to identify the graphics card I get the VGA led always turned on and the characteristic of (no vga found) long beep followed by three quicker.
I have tried an 550W and a coolermaster 700w psu with that card and they seem to work fine. I have also tested the psu on two other systems with a GTS 450 and another with a radeon hd 6xxx series and they work fine.
The real problem is when both of the gpu + psu are combined even on other machine (mobo).

Only thing that comes in mind is that the MSI draws more power than the other two older cards and the PSU fails to deliver that. So I guess that my PSU is faulty. Is there something am I missing here? How can I check my PSU if it is under-functioning? Thank you in advance.