I'm sorry to hear that you're having this issue.
You might check the settings in the video card, as well as making sure that you have the most up to date version of the software. With HDMI, the monitor is displaying the signal as it comes in. In some cases, overscan or other settings in the video card can cause this.
I just purchased a brand new SyncMaster BX2250 and hooked it up via HDMI to my ATI Radeon HD5770 graphics card. My display is set to the recommended resolution(1920x1080) but the image isn't filling the entire monitor. If I drop my resolution down a bit it fills the screen but doesn't look as good.
When I alter the image size settings in the monitor menu from Auto to Wide or back it doesn't seem to make a difference.
Can someone please help me out? I'm not sure why this isn't working and I'm thinking about returning the monitor if I can't get it to work.