1280x720p is too big in my TV LG LCD 32LC2R. WHY?!

Hello community.

I am using ForceWare 178.24 in CLONE mode
My TV supports 1280x720p and 1920x1080i

For desktop fit on the TV i have to create a custom mode with 1152x676.
Some games i tried don't allow to use custom modes and if i use 720p i can't see part of game information.
Same happens with 1920x1080i, gets too big, but i remember once using (i don't know wich driver version) 1920x1080i and it DID fit !!

So, is this a problem with my TV or with the drivers using incorrect parameters ?

Even if i could find the driver version that allowed me to use 1920x1080i correctly, in interlaced mode screen gets too much flickering its annoying, so 1280x720p is what i really need.

Any clues?
I am really desperate !!

Thanks in advance for anyone who can help me.