This bug only appears in JDK 1.3 train. It can't be reproduced in Merlin.
So file it as low priority.

The following is the demo code:

import java.awt.event.*;


public class robTest {

    public static void main (String args[]) {
        robotThread r = new robotThread();
        r.start();
    }

}

/* robotThread is used to control key press sequences. */
class robotThread extends Thread {
    private java.awt.Robot rob;
    private static int INTERVAL = 10;
    public robotThread() {
        try {
            rob = new java.awt.Robot();
        } catch (java.awt.AWTException e) {
            System.err.println("Failed to create Robot.");
        }
    }
    
    public void run() {
        System.out.println("Robot started");
        try {
            sleep(INTERVAL * 1000);
            rob.keyPress(KeyEvent.VK_ENTER);
            System.out.println("Enter Key Pressed");
            rob.keyRelease(KeyEvent.VK_ENTER);
            System.out.println("Enter Key Released");
        } catch (InterruptedException e) {
        }
    }
}


compile it and run it. Program will hang after the Enter key is released, using
1.3* release. Program will exit using Merlin.

The following is the thread dumps:
Solaris:
=========
[comanche:yuwang:tcsh:~/temp] > Full thread dump:

"Thread-1" prio=5 tid=0x282b8 nid=0x1 runnable [0..0xffbee320]

"AWT-Motif" prio=6 tid=0x1f2d88 nid=0xd runnable [0xf4601000..0xf46019e0]
        at sun.awt.motif.MToolkit.run(Native Method)
        at java.lang.Thread.run(Thread.java:484)

"SunToolkit.PostEventQueue-0" prio=6 tid=0x1e6fe0 nid=0xc waiting on monitor [0xf4701000..0xf47019e0]
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:420)
        at sun.awt.PostEventQueue.run(SunToolkit.java:497)

"AWT-EventQueue-0" prio=6 tid=0x1e6eb8 nid=0xb waiting on monitor [0xf4801000..0xf48019e0]
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:420)
        at java.awt.EventQueue.getNextEvent(EventQueue.java:254)
        at java.awt.EventDispatchThread.pumpOneEvent(EventDispatchThread.java:101)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:84)

"Signal Dispatcher" daemon prio=10 tid=0x97f10 nid=0x9 runnable [0..0]

"Finalizer" daemon prio=8 tid=0x94748 nid=0x7 waiting on monitor [0xfd181000..0xfd1819e0]
        at java.lang.Object.wait(Native Method)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:149)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
        at java.lang.ref.Finalizer$FinalizerWorker$FinalizerThread.run(Finalizer.java:120)

"Reference Handler" daemon prio=10 tid=0x92e10 nid=0x6 waiting on monitor [0xfd281000..0xfd2819e0]
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:420)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:129)

"VM Thread" prio=5 tid=0x921b0 nid=0x4 runnable

"VM Periodic Task Thread" prio=10 tid=0x96588 nid=0x8 waiting on monitor


Windows:
========
Full thread dump:

"Thread-2" prio=5 tid=0x234598 nid=0x4d8 waiting on monitor [0..0x6fb30]

"AWT-Windows" prio=7 tid=0x827e28 nid=0x5a0 runnable [0x8e0f000..0x8e0fdbc]
        at sun.awt.windows.WToolkit.eventLoop(Native Method)
        at sun.awt.windows.WToolkit.run(WToolkit.java:188)
        at java.lang.Thread.run(Thread.java:484)

"SunToolkit.PostEventQueue-0" prio=7 tid=0x827720 nid=0x5bc waiting on monitor [0x8dcf000..0x8dcfdbc]
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:420)
        at sun.awt.PostEventQueue.run(SunToolkit.java:491)

"AWT-EventQueue-0" prio=7 tid=0x8a9c38 nid=0x5b8 waiting on monitor [0x8d8f000..0x8d8fdbc]
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:420)
        at java.awt.EventQueue.getNextEvent(EventQueue.java:260)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:106)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:98)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:85)

"Signal Dispatcher" daemon prio=10 tid=0x8001c0 nid=0x5b0 waiting on monitor [0..0]

"Finalizer" daemon prio=9 tid=0x8990ec0 nid=0x5a4 waiting on monitor [0x8c4f000..0x8c4fdbc]
        at java.lang.Object.wait(Native Method)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:108)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:123)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:162)

"Reference Handler" daemon prio=10 tid=0x8990238 nid=0x578 waiting on monitor [0x8c0f000..0x8c0fdbc]
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:420)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:110)

"VM Thread" prio=5 tid=0x89fe088 nid=0x5c0 runnable

"VM Periodic Task Thread" prio=10 tid=0x7fee98 nid=0x5a8 waiting on monitor
"Suspend Checker Thread" prio=10 tid=0x7ff810 nid=0x5ac runnable

###@###.### 2001-10-23