if it is changing the aspect ratio you can stop this by taking this off auto and putting it on manual -whatever mode you want it to be on. if changing tv channels causes it (or during adverts) this should fix the problem. different shows and adverts are broadcast in different ratios and tell the tv how to display them correctly, this causes your tv to change aspect ration.
if it is doing it during shows or when using the ps3 and nothing is changing and putting the ratio on manual doesn't fix this then i don't know!
in case you don't know what i mean by the ratio, tvs call the different settings different things, my sony remote has a picture of a screen with different rectangles in it, settings can be called "zoom", "full", "smart", 16;9, 4:3, etc
borris the magician, December 2009