JDK/JRE: 7 b147 32 bit
OS/platform: UEL/OEL 6.* x64

The following code throws NPE:

public class Test {
  public static void main(String[] args) throws Exception {
    javax.swing.UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
  }
}

Output:
Exception in thread "main" java.lang.NullPointerException
at sun.font.FontConfigManager.getFontConfigFont(FontConfigManager.java:352)
at sun.awt.X11FontManager.getFontConfigFUIR(X11FontManager.java:817)
at sun.font.FontUtilities.getFontConfigFUIR(FontUtilities.java:484)
at javax.swing.plaf.nimbus.NimbusDefaults.<init>(NimbusDefaults.java:138)
at javax.swing.plaf.nimbus.NimbusLookAndFeel.<init>(NimbusLookAndFeel.java:100)
at com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel.<init>(NimbusLookAndFeel.java:32)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at java.lang.Class.newInstance0(Class.java:372)
at java.lang.Class.newInstance(Class.java:325)
at javax.swing.UIManager.setLookAndFeel(UIManager.java:576)
at Test.main(Test.java:3)

It is the reason of failure of the following JCK test:

api/signaturetest/sigtest.basic.html#basic