Strange video problem on boot

I have an odd problem with a new GPU card where I get no video signal on power up but as soon as Windows load the graphics driver, the monitor turns on. My system is self built and has been running fine until recently when I seemed to have a problem with the existing GPU, hence the warranty replacement. My system is:

Motherboard: GA-X58A-UD3R Rev 2.0
CPU: Intel I-7 950 @3.07GHz
GPU: MSI GTX 670 PE OC
Memory: 3*4GB Crucial DDR3
PSU: Coolermaster RS-850-SPHA-D3 850W: +3.3V:22A, +5V:25A, +12V:70A

Now I've already run through a swathe of tests and can confirm that all the components are working. Tried GTX 670 in another system and it works fine, tried an NVidia Quadro in the above system and it works fine - I see video from power up to Windows 7 login screen. I've tried different DVI cables and this makes no difference - the cables I am using are good.

Next, I have a KVM so I put both the GTX 670 and the Quadro into the system and cabled their DVI O/P to separate ports in the KVM. This is where the fun starts. NOTE: there is no onboard video so I need some way to see the BIOS and boot screens, hence this setup.

Some background on the motherboard. It has a BIOS setting that defines what PCI slot will be used as the initial display port. This can be set to PCI, PCI-E, slot 1 and PCI-E slot 2. As long as I put the Quadro in slot 1, I can use the PCI and PCI-E slot 1 BIOS settings and I will get video from power up but the GTX 670 does not produce a signal until Windows loads its driver at which point the monitor turns on and I can login to Windows using the GTX 670 as my display. If I swap the cards around, I don't get a video signal at any time and no matter how long I wait Windows does not appear to boot. If I change the BIOS setting (with the Quadro in slot 2) to PCI-E slot 2, then I do get video.

Finally if I remove the Quadro it is irrelevant what the BIOS setting is. I get no video signal on power up until Windows boot loads the GTX 670 driver and from that point I can work normally. I've googled extensively but haven't found anything close to this, some similar and none of the solutions are relevant to my problem.

I have upgraded the vbios on the 670 but have not been able to find the latest BIOS for the motherboard. I've tried using the Gigabyte BIO update tools but (a) the Bios tool doesn't list my motherboard (b) another tool lists my motherboard as revision 1.0 but it is clearly marked on the board as revision 2.0 (c) they list the BIOS version as FB but on the download site there is no FB revision for either revision 1 or revision 2 motherboards so reluctant to try flashing any of the later BIOS versions.

I'm thinking of buying a cheap GPU just so I can get into BIOS or the Windows boot menu when I need to if I can't track down the problem, so any suggestions would be gratefully received. BTW, I have cleared the CMOS and reset the BIOS multiple times but it makes no difference.

Many thanks,

George
 
Seems the problem may lie with the card. After exhausting and eliminating all causes I could think of, the last thing I thought of to try was to connect to my TV using the HDMI socket on the card. This provides a video signal from power on but using the DVI socket I don't get video until Windows has loaded the GTX 670 driver.

Any ideas why the DVI socket is fine when I use the NVidia Quadro but doesn't provide a video signal in standard VGA when I use the 670?
 
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