Buddypress - new site tries to use default wp theme instead of the buddypress theme.

Hi,
I have in setup a WPMU with Buddypress, and set the the default Buddypress theme as the network theme, and deactivated the default WP theme. But when I make a site it still uses the default WP theme(twentyten). When I delete that theme new sites become completely blank.

How can I make it so that new sites use the Buddypress default theme?