I'd try the following. If one doesn't work, try the next one:
- Try a CMOS reset on your mobo. Unplug the pc from power and remove the CMOS battery for at least 5 mins or so.
- Try removing and re-seating the GPU.
- Try removing and re-seating the RAM.
- Try removing the boot drive and booting. If you get video output, then it's likely a Safe Mode / HDMI issue. You can also try the other video ports.
- Try the other ports on your GPU. Sometimes video will only output to a specific port.
- If your mobo has video outputs, try those. Sometimes video will only output to a specific port.
- Try a DVI => HDMI adapter. I'm not sure if an adapter would be enough to overcome the Safe Mode HDMI incompatibility, but it's worth a try.
In a worst case scenario, I suppose the "Fast Timings" setting could have damaged the GPU. In this case I would RMA the card. If RMA is not possible, you can look into flashing the GPU BIOS, but I'd only do this as a last resort.