Just so you know, your site is not actually gone. It's just got server errors going on which is why you see the white screen. None of your data is actually lost, it's just not accessible until you fix the errors.
I would start by deactivating all plugins, make sure the site works, and then activate just buddypress. Test again, if it works, then reactivate plugins one at a time until you find the culprit.
Also, it would help to know what vs. of buddypress you started with and what vs. you are trying now. Also what vs. of wordpress.
If all else fails, simply revert to your backup... guessing you weren't dumb enough to upgrade a live site without a complete file and db backup first.....
If you check the bp site, you will see tons of people having major problems with the bp update. Basically the latest version is messed up big time.
If you do deactivate all the plugins, and still have problems then at least you know it's not a bpdev plugin causing any issues.
Part of the problem is that bp made such major changes in the updates, that almost every plugin out there is going to break. Even bp itself does not work properly right now.
good luck, I'd stay to help but it's 2am and bedtime.