Strange exception

I've encountered a seemingly random exception that only reproduced once.

Background: we are using several connectionlisteners simultaneously, managed in separate threads. Caught it on Acer A100 Iconia Tab tablet, Android OS 3.2, latest Lightstreamer android client.

Here is the stacktrace:

Code:

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11-29 10:42:30.870 E/AndroidRuntime( 7765): FATAL EXCEPTION: Stream-sense queue

11-29 10:42:30.870 E/AndroidRuntime( 7765): java.lang.IncompatibleClassChangeError: interface not implemented

11-29 10:42:30.870 E/AndroidRuntime( 7765):        at com.lightstreamer.ls_client.ExtConnectionListener.onNewBytes(ExtConnectionListener.java:129)

11-29 10:42:30.870 E/AndroidRuntime( 7765):        at com.lightstreamer.ls_client.ExtConnectionListener$5.run(ExtConnectionListener.java:131)

11-29 10:42:30.870 E/AndroidRuntime( 7765):        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1081)

11-29 10:42:30.870 E/AndroidRuntime( 7765):        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:574)

11-29 10:42:30.870 E/AndroidRuntime( 7765):        at java.lang.Thread.run(Thread.java:1020)

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The exception is strange also for us.
The reported line (ExtConnectionListener.java:129) contains a method call on a class that must have been supplied by the JDK since java 5.
However, other invocations of that method must have been performed before the specified one.
I can only expect a JVM bug, perhaps a race condition as the class is being replaced by some bytecode optimization process.
Did you see the exception always with the same stack trace?