So everyone running MOSS works with libraries, and working with office files stored on libraries. Most of the times it works as a bliss, but there a few notes. Within the naming of folders in your library NEVER use the following characters, since while your SharePoint works nicely with them, your Word or PowerPoint will actually fail trying to open the file, giving you an error that it cannot be read.
Just refrain from using these characters either in your filename, folder name or anything else that goes in the url. And make sure all your users know about this.