BuddyPress.org

I have installed Buddypress on a subdomain http://mysite.mydomain.com and noticed that in IE9 the CSS for the navigation is broken:

http://www.neiloughton.com/BuddypressScreenCapture.jpg

Can anybody else confirm this or offer a fix? The error shown does not occur when installed at the root of the domain or in a sub folder.. only on a sub directory..

I noticed this issue as i was using a child theme based around the default and presumed it was something around my code.