Like most things where you are only going by a "noise" someone posts on here, it is pretty hard to tell. A few things that jumps to mind - the pads weren't relocated properly. If new pads were put on - they haven't bedded properly. Also pads after they are put back in can do with some "anti-squeaking" compound on the back of the pads (worked wonders on an old prelude I once had).
Could be a bunch of other things - but most importantly, if these thieving wankers are looking for $300 to replace one rotor - DO IT YOURSELF!!! Not sure of regular prices but marlows here in the west were advertising brand new rotors for EA's a few months back for $60. Don't know about you but it sure as hell doesn't take 4 to 5 hours to put one rotor on an EA. These guys are taking you from a ride from where I am sitting.
Good luck with it,