I came across this when I tried to tidy up a few files I'd imported that had a whitespace as the first character. When trying to rename, I kept receiving an error msg saying source & destination file were the same. This had me flummoxed until I tested by trying to create a file with a space as the first character. Win7 woudn't let me do it, as it auto removed the space.
Hence any attempt to remove a space from an *existing* file fails as Win7 sees them as one and the same, when in fact they're not.