Re: BuddyPress Upgrade Killed My Blog. HELP.
Disable all of your plugins – move them from the /plugins/ directory. Upgrade WordPress MU to the latest.
Re-add your plugins to the /plugins/ directory, do not activate them. Upgrade BuddyPress and then re-active your plugins.
Please, please backup before you upgrade. I’m not saying this for my own health. If you have a site running that can’t afford to be down, this is critical.