If anyone is interested all i did was go into CCC, go to "Desktop and Display" then right click the little monitor in the bottom left hand corner, click "configure", then go to the "HDTV Support" Tab. From there I selected "add 1080P50 Format to the display manager" and then click Apply.
The problem is actually a change in how refresh rate is managed in DX10 through WDDM, vesus D9, where control is given over to the app/game authors which sometimes is a bad idea since they don't support 'off resolutions/monitors' and it creates a problem since the old tools don't work anymore since they don't have access. Had this trouble when playing on work plasmas (fine at 1920x1080 & 1366x768 & 1280x720, but couldn't get it to work @ 800x600 on one of the old ones in one of the small lunchrooms [which was more soundproof for our laughing and cheering/jeering])
What model Regza exactly do you have?
Most likely the max resolution of your monitor IS 1280x720 and what it was doing @ 1080i was dithering between lower resolution fields to recreate the 1080 image.
It doesn't sound better running @ 1280x720, but that may actually be the highest image quality provided by the TV with 1080i doing some interpolative work that should show you a lower quality image when doing fast moving gaming/imaging.
Anywhooo, if you insist that 1080i is better then try windowed mode, it often fixes that where you can still output 1080i, that's what I had to do.
Nice, yeah they added that fixes a few Catalyst launches back but it still doesn't work on some games.
It forces TV vs Monitor detection via HDMI which sometimes doesn't send the EDID info to the card (thus not giving you options sometimes), but what you're essentially doing is having the card broadcast @ a specific resolution regardless of whether or not it's supported by the TV natively, and then it handles it like a 1080i/1080p broadcast and uses the on-TV hardware to interpret the input.
Now wheres that "solve" button???
You need to ask it as a question not a comment in order to have a best answer button which gives you a 'solved' tag.