Yup, it is indeed. There are several possible reasons behind this. Most likely at somepoint someone canceled a download of that video partway through and then shared it with theworld. That means that that complete hour of video simply isn't there in your file. Many video formats (Most notably asf) Contain and index in the file headers that give the supposed playlength. Although this results in a situation such as yours (note that the mpeg format does not use such a headera subsequently ussualy displays the correct playtime), it also prevents the unfortunate situation with many avi formats (which contain an index at the END of the file) where partial downloads often cannot be played at all without special software to rebuild this index.