Parts of Hard-drive files not showing, only on macbook?

Hey guys, I have a hard drive that has been running well until now. When I open a folder in Finder, which contains a large amount of files in it, only the first ten-ish are shown, the rest disappeared. But they are still there, because some missing files are music files imported into iTunes, and when I open iTunes, those "missing" music can still be played. Also, this problem doesn't appear on Windows, when I plug the hard drive on a Windows PC, everything is there again. Any idea what the problem might be? Thanks in advance.