Picture size

We were busy watching a programme when the screen size all of a sudden jumped smaller than the full screen. The height is correct but not the width, there is a gap on both sides. We looked in the manuals and tried the different settings and have selected full screen, auto settings etc but it does not change. Our 32" Hisense LCD is now a year old and has just gone out of guarentee, please assist. regards Doreen
doreens@mantellait.co.za