...not sure why you are seeing that error.
In order to use System Manager you need to configure secureadmin to use SSL. To do this:
san>secureadmin setup ssl
*follow setup instructions...
From server (running system manager 1.1r1)
1. Start system manager.
2. Click on add -> Enter the hostname/IP of filer. (it should appear in the left pane, and you should at this point be able to view its configuration + other administrative tasks)