Javac creates two exception blocks on every synchronized section. Second block violates VM spec 4.9.5 (handling exception in proteced code) and differ from sample from 7.14.
Moreover, if inside syncronized section happens additional monitorexit instruction, offset 21 throws an error and runtime hangs up because second exception block.
It happens on any java from 1.4.2 upto 1.6.0 and jrockit. Maybe i miss something...

MonitorExitFail.java:
public class MonitorExitFail
{
    public static void main(String[] args)
    {
        Object sync = new Object();
        synchronized (sync) {
            System.out.println("done!");
        }
    }
}

javap -c MonitorExitFail:
public class MonitorExitFail extends java.lang.Object{
public MonitorExitFail();
  Code:
   0: aload_0
   1: invokespecial #1; //Method java/lang/Object."<init>":()V
   4: return

public static void main(java.lang.String[]);
  Code:
   0: new #2; //class java/lang/Object
   3: dup
   4: invokespecial #1; //Method java/lang/Object."<init>":()V
   7: astore_1
   8: aload_1
   9: dup
   10: astore_2
   11: monitorenter
   12: getstatic #3; //Field java/lang/System.out:Ljava/io/PrintStream;
   15: ldc #4; //String done!
   17: invokevirtual #5; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
   20: aload_2
   21: monitorexit
   22: goto 30
   25: astore_3
   26: aload_2
   27: monitorexit
   28: aload_3
   29: athrow
   30: return
  Exception table:
   from to target type
    12 22 25 any
    25 28 25 any

}

###@###.### 2005-06-16 14:33:23 GMT