Thanks for posting!
Is this a new installation? Were you able to access the admin console prior to installing the v3 update?
Let's start by restarting the admin server. Open the Terminal app from /Applications/Utilities and run the following command:
fmsadmin restart adminserver
Once done, attempt to load the admin console again. If it still fails, we'll want to clear the Java cache next. Open the Java Preferences app from /Applications/Utilities, select the Network tab and click the Delete Files button. In the resulting dialog, make sure that Applications and Applets is checked and click OK.
If the admin console still fails to launch after that, disable all network cards through System Prefences -> Network, reboot and attempt launching with the NICs disabled. If it launches successfully, you should be able to reenable them and continue using the admin console.