Invalid pal header in Natural One

I’ve just installed the trial version of Natural One and started my first program. It’s a simple program - no databases, files, etc. Just a screen prompt and display, nothing fancy.

When I try to run it, I get this error:

java.io.IOException: Invalid pal header (possible reason: client runs with SSL/Server without SSL or vice versa)

Reason: network problem encountered

What does this mean? What do I do?