Since it appears that SpreadSheet does something horrible and you haven't shared that code with us, you should probably pare it down to the bare minimum (i.e. display a JFrame, close the frame), see if you can get that to work and continue from there.
Originally posted by Joe Ess: you should probably pare it down to the bare minimum (i.e. display a JFrame, close the frame), see if you can get that to work and continue from there.