Hey There,
Thanks for writing in!
Most often this is due to a lack of available memory. Could you review this article :
http://theme.co/x/member/kb/solutions-to-potential-setup-issues/
Each active plugin will use a chunk of memory, and if you have too many active you’ll eventually run out during a page request.
You can try increasing the memory by following these instructions :
http://codex.wordpress.org/Editing_wp-config.php#Increasing_memory_allocated_to_PHP
If that doesn’t work, you may need to contact your host about it.
Hope this helps!