I am also getting similar problem in buddypress. As sson as I activate the plugin and place key and secret of appp... I can't access admin .. though my website is still alive... but I can access admin side...
The message says "Server error
The website encountered an error while retrieving http://........./plugins.php?action=activate&plugin=facebook%2Ffacebook.phpIt may be down for maintenance or configured incorrectly.
Here are some suggestions:
Reload this webpage later.
DO anyone having same problem...
after that I deleted facebook folder and admin page is coming.. I installed plugin again but same thing happening.. Is there a bug in the code... wats happening actually ?????????????