Default [Q] KFHD7 HDMI to TV could not go full screen?

Hi fellow KFHD owners, I just had a strange experience trying to output video from the device via microHDMI to my TV. Basically it could not get the full screen and the resolution seems to be messed up as well. So in landscape mode, I have two black bars on each side of my TV screen.

I tried to play with my TV's setting (set as "just scan" which is the mode I always used for external devices, such as computer and tab). What puzzled me was that this same device used to output fine to this TV, I used it for Amazon Instant Video and the 720p HD videos played fine in full screen.

I'm on stock rooted and it's been a while since I played this device last time so my knowledge might be a little rusty. Can you guys give some advices pls?

Thanks.