Ok, I don't know what the peice is called so I'm going to try my best to expliain it.

On the Les Paul, the bar where you put the strings through (near volume knobs) is just below what I am talking about. The peice is in between the bottom pickup, and that other peice i just mentioned (where the strings go in). It has small sqaure things on it which the strings sit into. From EBGDAE these sqaures go higher (towards fretboard) to lower.

My question is what effect do these sqaures have? If one is moved, what are typical... symptoms?

I think mine may have moved because for some reason, whenever i hit the 15th fret on the DAE strings, there is a very annoying rattle, and hardly any sound comes from the string. On the AE strings, the sqaure things on the peice i was talking about earlier (what are these called) are MUCH lower than the others. I think this could be the cause of the rattle?

Anything else that could cause that problem around the 15th fret?

Thanks in advance
yeah i think it changes the action of the strings. just do the opposite of what you did to screw it up, that usually works.
It doens't sound like you have a saddle issue. It sounds like a fret issue.

Take it into a guitar shop and ask for them to check to see if it needs the frets re-leveled.
hmm ok... I thought for a while I may have reversed the saddle (flipped it when I took it off to change the strings). I was going to just take the strings off/ loosen and fix, but I was looking at pictures, and the squares (are these the saddles, or the whole bar the saddle?) are how they should be height wise relative to each other. I was thinking 1 or 2 particular squares moved, causing this sound, but I don't see taht likely.

So I think I will take it into a guitar shop. Theres a Long and McQuade about 5 minutes away anyway.

Thanks guys!
Tune-o-Matic Bridge! thats what the bar's called. The saddles were the squares... sorry, I get it now