Poor Image Quality with HDMI cable to TV

Hi,

A lot of people seem to have this problem, so I know this is somewhat of a re-post.

I bought an HDMI to HDMI cable today to connect my PC to my TV, which I have been using as my primary display.

The problem is, the image quality is vastly inferior to when I connect it using a VGA cable with a VGA-DVI adapter. The adapter came with my Sapphire Radeon hd 5770.

Any thoughts? I have tried many of the solutions I've read online, to no avail. If I set my desktop resolution to the TV's native resolution, the image quality is the same, but there is a black border around the image.

The hardware I am using is as follows:

Windows7 Ultimate 64-Bit
AMD Phenom II X4 925
Saphhire Radeon Vapor-X HD 5770
4gb ddr3pc-1600(I dont think you guys need this)

The TV is a Samsung LN-S2641d. Its native resolution is 1360x768,and it does 720p (which is what I want to run it at).

My graphics drivers are up to date and I am running the most recent version of ATI CCC.

Any help or insight would be great.

Side note: There are 2 HDMI ports on the TV, labelled "HDMI/DVI", which a Samsung tech support rep told me just means it'll work with an HDMI to DVI cable. My graphics card has 2x DVI out and 1x HDMI out.