503 Error when enabling APC after memcached

So I installed APC, I added extension=apc.so to /etc/php5/apache2/php.ini, restarted Apache & then got this error message on all pages:

Page Could Not Be Loaded

We're very sorry, but the page could not be loaded properly. This should be fixed very soon, and we apologize for any inconvenience.
Debug Info:

Status: 503
Response: Service Unavailable
XID: 806786216

Now I have memcached up and running, but they should be able to run together, right?

This could be a doc issue, but really not sure what I'm doing wrong here. Have been following the following:

http://www.thefanclub.co.za/how-to/how-install-memcached-on-ubuntu-for-d...
http://www.simplemachines.org/community/index.php?topic=354914.0