Perpetually running Java applet is stalled intermittently due 
to "killing sub-process because of no heartbeat reply".
This is only reproducible on IE browsers.

The issue can be reproduced on new Java Plugin of JRE 6 Update 18.
The error message (recorded w/ JRE 6 Update 10) on the IE browser 
side looks like follows:

[ ... ]
JVMInstance (1.6.0.10) processing HeartbeatMessage, recv ts: 434920815362, send ts: 434920815390, dT: 28
[ ... ]
JVMInstance (1.6.0.10) processing HeartbeatMessage, recv ts: 434930816346, send ts: 434930816358, dT: 12
[ ... ]
JVMInstance for 1.6.0.10 killing sub-process because of no heartbeat reply
JVM instance for 1.6.0.10 exited
JVMInstance.unregisterApplet for applet ID 1
  LiveConnectSupport.shutdown(1)
  LiveConnectSupport: released [BrowserSideObject 0x2710ae8] for applet 1
  LiveConnectSupport: released [BrowserSideObject 0x2745200] for applet 1
java.io.IOException: Error closing named pipes
        at sun.plugin2.ipc.windows.WindowsNamedPipe.close(Unknown Source)
        at sun.plugin2.message.transport.NamedPipeTransport.shutdown(Unknown Source)
        at sun.plugin2.message.transport.NamedPipeTransportFactory.dispose(Unknown Source)
        at sun.plugin2.main.server.JVMInstance.disposePipe(Unknown Source)
        at sun.plugin2.main.server.JVMInstance.dispose(Unknown Source)
        at sun.plugin2.main.server.JVMInstance.access$2600(Unknown Source)
        at sun.plugin2.main.server.JVMInstance$Listener.jvmExited(Unknown Source)
        at sun.plugin2.jvm.JVMLauncher.fireJVMExited(Unknown Source)
        at sun.plugin2.jvm.JVMLauncher.access$300(Unknown Source)
        at sun.plugin2.jvm.JVMLauncher$JVMWatcher.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)
Terminating Java Plug-In Pipe Worker Thread (Server-Side) due to exception:
java.io.IOException: Error 0 reading from named pipe, numRead 0, ReadFile ts: 43
4962650222, now ts: 434962680979, dT 30757
        at sun.plugin2.ipc.windows.WindowsNamedPipe.read(Unknown Source)
        at sun.plugin2.message.transport.NamedPipeTransport$SerializerImpl.read(Unknown Source)
        at sun.plugin2.message.transport.NamedPipeTransport$SerializerImpl.readByte(Unknown Source)
        at sun.plugin2.message.AbstractSerializer.readInt(Unknown Source)
        at sun.plugin2.message.transport.SerializingTransport.read(Unknown Source)
        at sun.plugin2.message.Pipe$WorkerThread.run(Unknown Source)
IExplorerPlugin.OnFrameWindowActivate(cAxControl = 0x3561278, true)
IExplorerPlugin.OnFrameWindowActivate(cAxControl = 0x3561278, false)
IExplorerPlugin.SetObjectRects(cAxControl = 0x3561278, left = 2, right = 1272, top = 2, bottom = 995)
IExplorerPlugin.SetObjectRects(cAxControl = 0x3561278, left = 2, right = 1272, top = 2, bottom = 995)
IExplorerPlugin.OnFrameWindowActivate(cAxControl = 0x3561278, true)
IExplorerPlugin.OnSetFocus(cAxControl = 0x3561278)
IExplorerPlugin.OnFrameWindowActivate(cAxControl = 0x3561278, true)
IExplorerPlugin.OnFrameWindowActivate(cAxControl = 0x3561278, false)
[ ... ]