What's with the black bars?

[Getus]

My ps3 brokedown on me a couple of day's ago. So it is now for repair to sony.

So 1 hooked on my ps2 to my 42ich panny plasma (1080p) and i noticed that there are black bars around the screen. i tought this was due the screen being 1920x1080 pixels, and the ps2 can't fill the whole screen.

So i went over to a friend of mine, and put in the same ps2 game in his ps3 with the up-scaler on. BUT there where still black bars, they have different size but they are stil there. for the info my friend has the same tvset as i have.

So my question is how come that there are black bars with the ps2 on a hdtv. Even if you upscale it whit the help of a ps3?
Can it be fixed if i use a component cable for the ps2? because i use a rgb-scart cable.