NullPointerException

[3-417.3 Ales Pour]

Hello,
I'm trying to run xelfi (IDE for Java Development[jdk102] 
www.xelfi.cz) under kaffe 0.8.4 (biss-0.87) on linux and I get this 
message:
java.lang.NullPointerException
  at biss/awt/kernel/Toolkit.createPeer(line unknown, pc 0x82b0ec8)
  at biss/awt/kernel/Toolkit.createFrame(line unknown, pc 0x8280101)
  at java/awt/Frame.addNotify(90)
  at java/awt/Window.pack(97)
  at xelfi/top/XelfiLogo.show(32)
  at xelfi/Xelfi.main(37)
Has anyone ever got similar message and perhaps know what's wrong?
Thank you.

Ales