quick time conversion

Hi

I just bought my first FCS2 a few weeks ago and tried to compress a few videos for you tube. I exported to QT and than to MPEG4 and followed the instructions I found on your user group .
All went well but the video ended up cropped on the sides with a black bar on both sides.I noticed that my previous video's , edited with imovie ended up with 320x235 dimensions , now, they end up 300x240
Where did I go wrong? here's the test clip;