First boot up -- nothing displayed on monitor. Please help!

[MogTM]

I just finished putting together a computer with these components:
Motherboard: GIGABYTE GA-MA790XT-UD4P AM3 DDR3 AMD 790X ATX AMD Motherboard $139.99
Video Card: HIS Hightech H489F1GP Radeon HD 4890 1GB 256-bit PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card $234.99
RAM: Patriot Viper 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Dual Channel Kit Desktop Memory Model PVS34G1600LLKN $89.99
Optical Drive: Sony Optiarc 24X DVD/CD Rewritable Drive Black SATA Model AD-7240S-0B - OEM $25.99
Hard Drive: Western Digital Caviar Black WD1001FALS 1TB 7200 RPM SATA 3.0Gb/s 3.5" Hard Drive - OEM $99.99
Processor: AMD Phenom II X4 955 Black Edition Deneb 3.2GHz Socket AM3 125W Quad-Core Processor Model HDZ955FBGIBOX $245.00
Power Supply: CORSAIR CMPSU-650TX 650W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 $99.99
Case: COOLER MASTER RC-690-KKN1-GP Black SECC/ ABS ATX Mid Tower Computer Case $74.99

When I finished assembly and attempted to boot my computer for the first time, nothing displayed on my monitor. The fans on the PSU, the CPU and the GPU were all working, as was the optical drive. I know the monitor works with other computers. I initially suspected I had not made a good connection either between the graphics card and the motherboard or between the monitor cord and the graphics card. I checked (and tightened) both of these connections with no change. Is there anything else that could be causing this issue? Is there any way to check the above connections to see if the problem lies elsewhere?

Thanks for your help -- I enjoyed the build process, but will be very sad if I don't have a computer to show for it.

[shadowpr]

PROBLEMS with a NEW BUILD? Try This!!

Make sure if your video card requires a 6pin pci-e power cable that you plugged it in.