To make a long story short, isDisplayChangeSupported() is returning false and that revealed a bug in another method. So thats why it worked a long time ago, and then wasn't working now. Anyone know why thats returning false on win2k? :/
I can´t say why it does but I can verify that it also returns false on my win2k system. Had the similar problem that my code stopped to work, and it was becuase I had been writing the fullscreen mode change code on NT4 and when I tried it at home nothing worked. So I have disabled the check of isDisplayChangeSupported() in my code.