Re: Missing CSS in trunk theme upgrade
I assume that you are running on the bleeding edge, that you reinstalled the most recent BuddyPress trunk. The name of the parent theme was changed in r1843 and many new improvements made to the overall new parent/child theme architecture.
As the above referenced changeset indicates, the first step you should try is reactivating your theme. If that does not do the trick, then since you’re using a customized parent/child theme, you need to make sure that you carefully inspect the new default parent/child theme and find were any changes might have been made.