Hi guys!
In the first place I would like to thank the devlopers of Cog for a great application. 
While it isn't yet v. 1.0 it still has some glitches. The problem I ran across is when the cuesheet encoding for and ape/flac file does not match the current system encoding. In my case, there's a file with Latin ISO characters in it's filename, but the cuesheet is interpreted as Cyrillic. I. e.:
Real filename: Nguy