Glad I found this thread! Keith's suggestion of eliminating use of quotes in tags area was spot on. I removed the quotes and video now uploaded successfully.
I also was baffled at why publishing my video from iMovie to youtube would not work. No error, just would hang. I use an iPad 3 with iMovie for iPad ($4.99 download). After editing my video I was ready to upload. Filled in all the info in youtube upload area (title, description, tags (including quotes around phrases) as well as changing defaults to HD and public). After watching the progress bar reach the end, the process would just hang without any error being displayed. Tried redoing a few times, but same hanging result.
Once I found this thread, I said why not try and remove the quotes in the tag section...and amazingly, it worked perfectly...upload completed after the progress bar was finished. Marvelous! I will then go to YouTube to update the keyword phrases in quotes
Thanks Keith... Who would have thought the quotation marks were the culprit