Daytek 46" LCD TV DT4660 model?

Hi, my name is keith, and i have a problem with my 46" LCD Flat screen. It seems the only way i can watch the T.V. clearly is when i use the pip button to swap t.v. and either a video game or DVD movie going. The small screen will show the program fine being either t.v., movie or game, but as soon as it's supposed to show on regular screen it either comes out distorted or a blank screen. When i turn the T.V. on it shows the same, either a very distorted screen or blank, but the sound is still fine. What could this problem be contributed to, if you could please let me know i would really appreciate it. I may have to get a t.v. repair guy over, but i know that they may charge so much. My T.V. again is a Daytek 46" LCD DT4660 model. Thanks.