This is a spurious error... but it happens regularly.
Windows NT will launch an applet, but the applet window remains blank. It is not painted. If you clone that applet, the clone works fine. Restarting works fine also. To reproduce, launch many AWT intensive applets- one will eventually show this behavior.

[Tim, 5/24: Recategorized to classes_awt. This sounds like an AWT painting problem,
not necessarily a runtime problem (although it still could turn out to be caused by a
runtime problem).]