Have you tried printing out the file and looking at it with a hex editor? Maybe it'll help knowing exactly what that character is, then you could try tracking down where it's coming from (or just regex it out).
Comment on Re: Mysterious Whitespaces between each character in a file
Agreed. One possibility is that is contains a non-breaking space (ASCII code A0). /\s/ does not match this. Looking at the data with a hex editor will tell you if this is so.