PS3 screen display... How to fix it?

I have my ps3 connected to a 26 inch LCD tv... With an hdmi... I have always played perfectly and Looks awesome.... Yesterday i turned on the ps3 and the screen had black bars left and right of the screen so the picture of the tv looked square and not wide as the lcd tv should look.. I looked in settings and couldnt fix it... Can someone help me plzz