BuddyPress.org

@opensourcelover: If that doesn’t work what is suggested by @pcwriter my suggestion would be to look at what is causing your JavaScript error on your page. Using firebug I can see you have one. The first port of call I’d suggest would to turn off all plugins and widgets. This could explain the difference in browsers or at least be a good next thing to try if no CSS is different.

I totally second and agree with @pcwriter about using a child theme. Only way forward if you are going to make changes like this.