FULL PRODUCT VERSION :
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
OSX Mavericks 10.9.1

EXTRA RELEVANT SYSTEM CONFIGURATION :
Macbook pro 2011 (dual graphics); external monitor plugged in; display mirroring enabled

Also tested on a 2008 Mac Pro with mirrored displays and get the same failure.

A DESCRIPTION OF THE PROBLEM :
When an external monitor is connected and display mirroring is enabled AWT fails to initialise, and the following exception trace is created:

dhcp-152-78-94-65:~ jon$ /Library/Java/JavaVirtualMachines/jdk1.7.0_51.jdk/Contents/Home/bin/java Test
Exception in thread "main" java.lang.NullPointerException
at java.awt.Window.initGC(Window.java:467)
at java.awt.Window.init(Window.java:487)
at java.awt.Window.<init>(Window.java:536)
at java.awt.Frame.<init>(Frame.java:420)
at java.awt.Frame.<init>(Frame.java:385)
at javax.swing.JFrame.<init>(JFrame.java:180)
at Test.main(Test.java:5)

REGRESSION. Last worked in version 6u43

ADDITIONAL REGRESSION INFORMATION:
java version "1.6.0_33"
Java(TM) SE Runtime Environment (build 1.6.0_33-b03-424)
Java HotSpot(TM) 64-Bit Server VM (build 20.8-b03-424, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile the following Test class, and run it with display mirroring enabled:

import javax.swing.JFrame;

public class Test {
        public static void main(String [] args) {
                new JFrame();
        }
}

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
A window appears
ACTUAL -
A NullPointerException occurs in AWT Window initialisation:

Exception in thread "main" java.lang.NullPointerException
at java.awt.Window.initGC(Window.java:467)
at java.awt.Window.init(Window.java:487)
at java.awt.Window.<init>(Window.java:536)
at java.awt.Frame.<init>(Frame.java:420)
at java.awt.Frame.<init>(Frame.java:385)
at javax.swing.JFrame.<init>(JFrame.java:180)
at Test.main(Test.java:5)

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" java.lang.NullPointerException
at java.awt.Window.initGC(Window.java:467)
at java.awt.Window.init(Window.java:487)
at java.awt.Window.<init>(Window.java:536)
at java.awt.Frame.<init>(Frame.java:420)
at java.awt.Frame.<init>(Frame.java:385)
at javax.swing.JFrame.<init>(JFrame.java:180)
at Test.main(Test.java:5)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.JFrame;

public class Test {
        public static void main(String [] args) {
                new JFrame();
        }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
No workaround found for JDK7. Works as expected in JDK6.