Back in July, YouTube began enabling a new uploader for resumable uploads for certain browsers.
YouTube's David just gave us an update via the YouTube Help forums that they have made updates to the feature and are now supporting Internet Explorer, in addition to Chrome and Firefox 4+.
David is asking users to give it a try. If you use Chrome or Firefox 4+, go to the standard YouTube uploader and begin uploading a video. Then stop the upload by throwing your computer against the wall, okay - if that is not an option, then just quit the browser or disconnect from the internet. Then after you get your computer back up and running, start the upload again and it should pick up.
If you are running Internet Explorer you will need Silverlight and then you need to go to a special URL at upload.youtube.com/my_videos_upload?restrict=silverlight to use this feature.
There is nothing worse in the YouTube world than uploading a video for an hour only to find out that it stops when it is 99% done uploading because you accidentally quit your browser, your internet died or your computer froze.
Forum discussion at YouTube Help.