Threaded Replies Don't Work (Reply Button does nothing)

Hi there,

I have BP_ENABLE_MULTIBLOG enabled and thus am using Buddypress across my network.

On this site, when you click 'reply' to a comment the browser window moves but no message box appears to type in.

http://drumcovers.tv/groups/drum-covers/

However, on a different site (one displaying the same content from that group) it works just fine. For instance:

http://drummersdatabase.com/community/groups/drum-covers/

I've tried deactivating plugins to no avail which leads me to believe it might be a theme related issue.

Is there any way to find out what might be causing this?

Thanks!