roblob,
At this point, there is something drastically wrong with your rig. You may have fried something with your over clock... that said, let's try something else.
Take your motherboard out of the computer, strip EVERYTHING off of it, including HDDs. Put the mobo on the cardboard box it came in (or suitable replacement) or the static-free envelope the mobo came in. Now clean off the CPU, re-install it and re-paste it, Add the HSF and plug it into the CPU fan header. Add GPU (plug in it's power lead), one stick of memory in slot 1, the monitor and keyboard/mouse, then add the PSU 20/24 pin plus 4/8 pin power leads and prepare to turn the PSU on. You may need to hook up the case's power switch or short out the power switch's posts on the mobo (where all the case leads hook up). Now turn on the PSU and hit the start switch. What happens? You should get one beep only. Does your BIOS come up?
If BIOS appears, you're back in business. Shut down. Add one remaining component only at a time and re-boot each time. If any item causes a problem, that's a culprit.
If the board doesn't boot into the BIOS, you've isolated to the mobo, CPU, PSU, or GPU. To solve that issue, you'll need to check one replacement at a time. Have you got replacements for any of those from an old machine? You can buy a PSU checker cheap at Radio Shack for about $20. Call Gigabyte tech support and explain to them what's happening, ask for a cross-ship RMA for the mobo, see if they'll do that. They may ask for you to send back for testing.
Sometimes over clocking comes with a price - it will fail a marginal item. Just have to figure out what item
Good luck, Noel