Its doubtful that it would be a physical problem with your board. Maybe have a look at this older thread with a similar board to your. I think I remember reading somewhere the G45 can do 6 cards, while the G65 can do up to 7...https://bitcointalk.org/index.php?topic=97154.20]Gigabyte%20Z77A-G45
but might be wrong and its the higher model that can do up to 7.  I'll find out later next week when I get a G65 to play with.

Yes, bitcoin GPU mining is long dead. But GPU's are still used (and profitable) for scrypt mining like Litecoin, Feathercoin and other altcoins. Also depends greatly on your local electricity costs.

As a followup to the ops question I was able to get 6 GPU's working on my gigabyte board with a "little" messing around in win7 x64. I'll be getting the exact same board as you next week so I will be shooting to hit 7 too. http://www.gobitgo.com/articles/1002/How-to-Mine-with-6-GPU/ has similar info that may be a helpful reference. In the link above the author is using windows 8 but the procedure is the same and works just as well in windows 7 x64.

Here's my version of how to get 7 cards working on win7x64:

1) Install 12.6 drivers. - shutdown
2) Unplug all risers, then plug in 1, boot to windows, insure the card shows up in device manager. After its detected and confirmed there, shutdown and plugin the next riser closest (left to right or right to left) and verify in device manager. If the card last plugged in does not show up it most likely means you will need to make a jumper to short the pcie pins. There is a thread on these forums outlining the procedure if needed.
3) Continue verifying all the cards and jumper the ones as needed. After you make it past card 5 you will see cards 6 and above show the yellow exclamation showing a problem. No worries on to the next step.
4) Download 13.1 drivers and double click to extract.
5) Do not install drivers after initial extraction. Click cancel to exit the installer.
6) Back to device manager and we need to update the driver on the devices with the yellow exclamation marks
7) Manually update the driver using the the 13.1 drivers which extracted to C:\amd\13.1... (you can follow the instructions in the link above if you need more specific details)
8 ) This installation/update does take a few minutes so be patient and don't try and close the device manager or updater.
9) On to the next one, same procedure if you have 7 cards.
10) DONE
10) Start Mining already!  

Windows 7 X64 supports up to 8 GPU's. You'll have to use 12.6 or older drivers. 12.8 and later only support up to 4 GPU's. Use the catalyst removal tool before installing the new driver. You may also need to "jumper wire" your individual PCIE slot in order for it to work.

Canary would you mind PMing me when you're back. Interested in your bulk rate for blades. I don't think it was mentioned how many blades will fit into a large flat rate box for example, or is there a better way to ship them in bulk? Thanks.

You've got PM

Hi John, have you got your PM box set to "ignore n00bs" again! If you've got a moment I've got a biiiiig contract for you. Thanks.

That's a very low hash-rate for either crypto. For scrypt you should easily hit 600kh+, 12.8 drivers + 2.7SDK for example, 1050mhz, 1450mhz clock.

No it will not be profitable to run the thing at that rate. KNC will be realeasing a newer model next year to replace their first gen model. It's always an invest and re-invest in the next gen trying to keep up with technology (and stay profitable). Pretty much impossible but that's the idea.

It might be worthwhile to build a LTC rig, depends on alot of factors. They can certainly be time consuming and lots has to be taken into account if you are putting a few together. Go to coinwarz.com and use their calc, look at litecoin hardware mining comparison to get a sense of expected hashrates, its pretty easy to see what kind of return you'll get. Nothing is cheap or easy I'm afraid.