Hello all,
Yesterday I bought a new HP w2207h 22" monitor, it has both VGA and HDMI ports on it. My vid card is a SAPPHIRE Radeon HD 2600XT 512MB 128-bit GDDR3 PCI Express, and has 2 DVI ports. The card came with a DVI-to-HDMI adapter and says it supports HDMI on the box. The problem im having is that when i have the monitor connected through HDMI I cant get a picture unless the resolution is set at 800x600 or lower. As soon as i go to change it to anything higher the screen goes black and randomly flickers. Ive tried updating with the newest ATI drivers (standalone and Castalyst Control Center ones), i even tried installing the drivers from the HP CD that came with the monitor. The OS is Win XP Pro. The rest of the PC is only 5 months old which i custom built with high end parts.

hmmmm, it could be your adapter. I would try using one of these :
http://www.newegg.com/Product/Product.aspx?Item=N82E16812189129
I use one of these and dont have a problem.
Another way to check is to get another adapter (return yours for another or somethin) and check and see if it was that particular brand, or model or a defect. you never know with things.