I had a similar problem when using HDMI to connect to my tv. It would show that it was running in 1080p, but then the screen had this odd bar of unused pixels all around it. I tried adjusting the tv to fit the picture to the screen, but then everything came out all pixelated.
I'll try out my vga cable to the tv when I get home tonight and see if I can get it to fit properly or if I get the same thing you do.
No i don't have a good reason to use the HDMI, but it just looks so wasted to buy the cable when you're gonna rarely use it
Well just so you know, HDMI cables are normally used when you want to connect a TV to the PC or if you want to connect 2 LCD screens to one GPU assuming you only have one DVI and one HDMI cable. Of course you can always use the HDMI only if you want but as far as LCD panels go people normally use the DVI cable that is provided with the panel.