The Checkpoint firewall software runs on various hardware vendors.  For whatever reason they decided that to access the Checkpoint specific MIBs that a second SNMP agent would listen on port 260 of the device instead of including those MIBs in the main system SNMP agent.  This second agent can also be configured with a different community string.

NetMRI currently doesn't automatically guess that second community string.  If that second community string is different from the main system community string then it should be manually entered into the device viewer in the "Checkpoint Community" field.  If the community strings are the same then leave the field empty and NetMRI will use the community string it already has for accessing the main SNMP agent.