Problem: ugly program (no theme applied)
If you get an error like:

/usr/share/themes/Unity/gtk-2.0/gtkrc:41: error: lexical error or unexpected token, expected valid token

when you launch a java program under a GTK enviroment (GNOME) and the program looks really ugly or even it doesn’t start at all you may want to try the following..

Solution: Upgrade to the last 1.6 jdk.

To updgrade to the latest sdk in ubuntu follow this info:

sudo apt-get install sun-java6-jre

and select as the blessed ones:

sudo update-java-alternatives -s java-6-sun

check it:

java -version

If everything is ok launch you program 🙂

P.S.: Check that the program that you’re launching is not using a proper jre (so 1.5) otherwise all your effort will be useless.