Although it's not common, sometimes, my videos get stuck. If it's taking an extended amount of time, just abort the operation, and restart it again. That's what I do. It's only happened twice. I have 20 videos, so it's not all bad, I suppose. Try that.
One of my videos froze at 95%. I think disconnecting my computer from the internet while the upload was in process is what screwed the entire thing.
And, yes, you can turn your computer off after the video has been uploaded to youtube.