Hi Victor,
OEM is delivered with Oracle, but you need to install and configure it to use.
As you must have upgrade from 10g to 11g, and OEM was configured before the upgrade, so you are getting old version of it.
You need to check the package delivered for OEM and may have to re-install and configure for version 11.
http://docs.oracle.com/cd/E11857_01/install.111/e15838/upgrade_em.htm#CHDEJGAH
As, i have installed and configure this long ago on 10g, I can't really say about 11g.
Regards,