The preview of the site on the sign up page is squeezing the theme chooser as shown in the attached pic.
I think Profile Details Name (required) on the right is the issue. Is that to do with buddy press or is that part of the normal prosite wordpress sign up. I cant recall.
I have looked at it on firebug and deleting the Profile Details
in frirebug does then shows the full theme template preview from blog template.
Could you cast your eye over it.