Re: internal server error after activating bp
First of all, an Error 500 (internal server error) message usually means something is not working properly with one of the software components on you server. It is not directly a WordPress or BuddyPress issue.
I’m guessing it’s an issue with your PHP install. Forcing the server to run PHP 5 instead of 4 may do the trick–assuming your site is being served under PHP 4. This is just an initial guess. See these threads for more detail:
However, there could be something else causing the problem. What you need to do is distill your environment down to the lowest common denominator. Make sure WordPress is working fine by itself before installing BuddyPress. To do that, you deactivate all other plugins and test WP by itself. If it is working without issue, then you reinstall BP and activate. You should not have any other plugins besides BP activated and you should be using the default theme that comes with BP when testing.
By the way, I suggest doing a clean install of BuddyPress. This means making sure the entire BP directory is removed and then starting over with a clean install of BP. Of course, as always, backup any data before you do any upgrades or reinstalls.
If you do not have any issues with WP running only the BP plugin using the default BP theme, then you know it has something to do with a custom theme, one of your other plugins, or some combination of the two.
You then start going back up the ladder one step at a time. Switch the default BP theme to your custom theme. Does the problem return? It not, then is has to do with your plugins. Activate one plugin at a time until the issue returns.
But, with an Error 500, I’m guessing it is something outside of WP and BP causing the issue. Show the links above to your hosting firm. They are the only ones that can help you.
Also, as another resource, search the WordPress forums to see if anyone there has reported a similar issue.