Game throws illegal error when running through WebStart

My game works fine in fullscreenmode whenever I run it straight from the source code in my compiler…

Then I converted it into webstart, now it throws this nasty error

java.lang.UnsupportedOperationException: Cannot change display mode

why is that? can you like not change display mode with WebStart? I have all-permissions on too.

if needed i can post my code…

Have you signed your JARs?

yes I have signed my jars… i dunno what is wrong

here is my link to the jnlp

lightsoflifesoftware.n00bl33t.com/Gratorial/src/gratorial.v.2.1.jnlp

How are you creating the DisplayMode object? Are you creating it yourself or getting it from the list of available displaymodes?

sorry for the late reply, been away from the computer a while

I am getting the default screen device, im saving the resolution(display mode), and then i make my new display mode, and whenever they quit the program, it reinstates the old display mode.