Sound problems...

have you gone back to the original recording and listened to it?

if it is there too and was not a transfer problem...you have a problem.

there is nothing that can be done if it is in the original recording...and you will have to replace the dialoge for that scene...sucks i know...never a fun thing to do...

there is a cheap way to replace this, but you sill need your actors back...no other way around this...you can POOR MANS ADR the scene...just play back the scene...piece by piece for each actor and have them try to read the lines to the picture...it may take several tries to get a good match...you will have to do this for every actor in the scene...one at a time....and then lay in the newly recorded sound to the scene...and then lay in some abiance track to cover up the cuts...try to use the same mic that was used in the scene as this will make for a better match as well.

you really dont have another choise...other than going to a real ADR stage and doing this under better control....but the process is the same....only cost more.

if you are lucky...it was just a transfer problem...

hope this helps