Graph icons not showing up in Centreon

Ubuntu Server 12.04 x64
Nagois 3.4.1
Centreon 2.3.9
Nagios-Plugins 1.4.16
NDOUtils-1.5.2

I followed this excellent guide to install Nagios + Centreon from the ground.

After completing all steps and adding some Windows hosts to Centreon, the graph icons did not show up although I configured graphing at the service properties (except for ping).

Checking the logs revealed that in fact my db username was incorrect (it was Centreon instead of ndouser).

tail -n 5 /usr/local/centreon/log/centstorage.log

2012-10-01 16:37:49 - Error when connecting to database : Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
2012-10-01 16:37:51 - Error when connecting to database : Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
2012-10-01 16:37:53 - Error when connecting to database : Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
2012-10-01 16:37:55 - Error when connecting to database : Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
2012-10-01 16:37:57 - Error when connecting to database : Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

so I opened up ndo2db.cfg to correct the credentials then restarted Centreon.

sudo vim /usr/local/nagios/etc/ndo2db.cfg