Re: Errors in WPMU homepage and in reading alternate themes
Which version of BuddyPress are you running?
If you’re using 1.1-beta, then the bp-sn-framework and bp-default directories need to be moved into /wp-content/themes/.
If using an earlier version, then you need to move bphome into /wp-content/themes/ and bpmember into /wp-content/bp-themes/
Also, more suggestions about how to tackle your particular error message can be found here:
Just one note, if you get to the stage of deleting BuddyPress and starting over with its install, please make sure you deactivate it first before deleting it.