BuddyPress.org

Okay, is WordPress working fine before installing and activating BuddyPress?

Also, which version of WordPress and which version of BuddyPress are you using?

You need to look at your error logs to find out more details–both PHP and Apache logs. Your host should be able to give you access.

Finally, you can try adding this to the top of your .htaccess file:

### Set PHP directives ###

php_value memory_limit 96M

You may need to decrease that if your hosting company has not allocated that much memory for your account. You can try 60 then 30, for instance.