HelloThemes, for your info; I followed the installation instructions of HelloMix TO THE LETTER on two fresh installations of Mage 220.127.116.11 on two seperate servers, with the same distorted page layout.
I also managed to resolve the issue by removing the /app/design/frontend/default/default directory. Bizarre.
There is clearly an issue of some sorts with this theme 'out of the box'. I think you should investigate this further.
It's a great theme now I've got it running!
All the best