I have a media PC running Windows 7 x64. I am running an ATI HD 4600 to my receiver using HDMI for both video and audio. The video is connected to a 42" Magnavox 1080p LCD TV. The resolution is set to 1080p @ 25 Hz (60 Hz causes flickering, and the others are not supported by my TV).
Everything had been working fine, until recently, I'd noticed that the entire screen appears to be offset to the right by 3-4 inches. The vertical offset of the image is perfect.
My TV doesn't have image placement settings, and it scaling setting is set to "Unscaled", as it always has been.
I've upgraded to the latest Catalyst drivers, which only seem to increase the frequency at which I have to fix the overscan settings - the default settings do not cover my entire screen, and the Catalyst utility sees fit to change the overscan back to the default setting every time I change the resolution.
This problem is not reproduced when viewing either the on-screen menu for my TV, the on-screen menu for my receiver, or my XBOX 360, which is also connected via HDMI.
What could be causing the image to be offset when viewing my HTPC?