False error messages
For example, when you try to send an email with attached files, and a Microsoft application (like Word or Excel) has any of the attached files open, Microsoft Mail will say that it "cannot locate" the open files. This is false, because is not having trouble locating the files; it has simply been told that the files are in use. The false message causes distress, because the user might think the file has been deleted or misplaced. It causes confusion, because it implies that the files need to be found. To remedy this error, they need only be closed (in whatever application has them open); then the email can be sent.