Maybe you are right... I did edit the video in Windows Live Movie Maker, and I saved the video in one particular folder. Then, I did upload it to youtube (but I dont know which settings!) so maybe thats the reason.
In the other hand, if you see my other videos which I did not edited, they are in 720p.
I will try to upload it again and I will check the settings, maybe I will found what happened.
Thanks a lot!