YouTube and iSquint distortion

I "Shared" a video to disk using the "web" option, and it looks fine, albeit a little low-def (1 mb file size). But, when I uploaded it to YouTube it came out distorted, squashed into a square instead of a rectangle. I thought this was probably YouTube's fault but then I tried uploading the full quality video (around 180 mb) and YouTube rejected the format even though it was a .MOV.

So then I used iSquint to convert it to a medium-quality mp4 (8.6 mb). It came out distorted before I uploaded it to YouTube.

???