Hey guys- I have the ANSWER here....Trust me- it took the better half of the last 2 days to figure out, and I tried everything- even went to Apple Store and asked the guys there- they couldnt figure out why....Here's what you do...IF you have a Mac... the same programs....
You need to plug in iPhone 4 to your computer, then dowload into iPhoto first- as a movie...
THEN you need to export to iMovie
THEN you need to upload it to you YouTube. It will (finally) give you an option to upload in HD- any other way simply doesn't work, and I've tried ALL of the following options as well- without success..
Hope this helps...
Things that DIDNT work...(Apple if you are listening, your iMovie App does NOT convert it into 720)
Tried emailing the HD video to myself then uploading it to YouTube manually- it didn't show up in HD
Tried uploading the HD video directly to Youtube via the iPhone4- didn't work
Downloaded video into iMovie, optimized, but it wouldn't let me upload HD into Youtube.
Even tried the iMovie app for the iPhone4, exporting it as an HD (720p) movie, putting in camera roll, THEN uploading to YouTube. Didn't work.
Waited a day to see if it was just a processing delay for YouTube- no luck
Tried doing all of these things in the Apple Store WITH two Apple guys right next to me- didn't work
Also tried doing the same things with a different iPhone 4- didn't work..