We use IBM X systems, in this case a x3650 M2 and the java requirements for the IMM / RSA are a bit vague. I finally came across this IBM support page where workaround 2 solved the problem. That would be doing this:

• Add the IMM Internet Protocol (IP) address to the local intranet secure sites:
• From IE, select Tools –> Internet Options –> Security tab –> Local intranet –> “Sites” button –> “Advanced” button.
• Add the IP address of the IMM: http://192.168.70.125 (default)
• Clear the “Require server verification (https:) for all sites in this zone” check box.
• Select Close.
• Select OK.
• Select OK.
• Press F5 to refresh IE.
• Click Remote control.
• Click “Start Remote Control in Single User Mode” or “Start Remote Control in Multi-User Mode.”

The Java window will start with the remote control session and the Virtual Media Session.