graphics generated using awt.graphics not displaying when run through a jar

I've created a small application that works fine when compiled and ran normally.

When I create a jar and run it, the application works mostly fine too, the button (there's a button in it) shows up, but the graphics produced with java.awt.Graphics don't. What's really weird is that this problem only seems to occur for some people. I sent the jar to some friends and for some of them it worked fine, while others had the same problem I have.

Can anyone tell me what's causing this and what I can do to fix it?

[533 byte] By [SmurfZGa] at [2007-11-27 4:54:36]