Please make sure that you entered the exact same value for the hostname of vCenter into vCloud Director and vShield Manager. If you put an IP into vShield and a Hostname into vCloud, this will fail to match.
Basically, make sure to copy and paste from one to the other. I can post a picture when I get into the office.
Aside from this, if you are on vShield 5.1.x generation, please ensure to be on the 5.1.2a maintenance bundle.