Maby some other member can explain how to get AROUND this (I can't), but you can easily AVOID, it because for the Fligh By Night developers assignment it is not needed to install a security manager on the VM where the GUI runs.
Your GUI should run on a client proces, and your data server on a server process, and only for the data server process you need to install a security manager. When you run in non-networked mode, GUI and database in same VM, you do not need to install a security manager at all.
Hope this helps,
Henk van Jaarsveld