We encountered the same thing, same version (seems like any version) with Solaris 7. The JVM for some reason isn't ignoring the signal it receives when the user exits their session like it should.
We found that running the same as a normal user with sudo somehow bypassed the problem we were having.
You could also use the screen command if you keep having problems. Screen sets up a virtual text terminal, and you can attach and detach from it without affecting the running program.