FULL PRODUCT VERSION :
java version " 1.7.0_25 "
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) 64-Bit Server VM (build 23.25-b01, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]
Microsoft Windows XP [Version 5.1.2600]
Linux stus-box.site 3.7.10-1.16-desktop #1 SMP PREEMPT Fri May 31 20:21:23 UTC 2013 (97c14ba) x86_64 x86_64 x86_64 GNU/Linux
Darwin localhost 12.4.0 Darwin Kernel Version 12.4.0: Wed May 1 17:57:12 PDT 2013; root:xnu-2050.24.15~1/RELEASE_X86_64 x86_64

A DESCRIPTION OF THE PROBLEM :
If a Web Start application registers a SingleInstanceListener, and that application is launched using dtjava and setting the jnlp_content variable, the second instance of the application blocks after displaying the splash screen until after the first instance has exited. After the first instance exits the second continues to launch. If the jnlp_content variable is not set the SingleInstanceListener of the first instance is invoked as expected.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create a simple application that registers a SingleInstanceListener with the SingleInstanceService. Perhaps one that simply shows a frame and exits when the frame is closed.
Create a simple HTML page that launches the application with dtjava. Launch the application with dtjava.launch({url: <url>, jnlp_content: <b64_encoded_jnlp>});
Launch the first instance of the application leaving the application running.
Launch the second instance of the application. The second instance will show the splash screen. After some time the splash screen will disappear.
Exit the first instance. The second instance will now continue launching.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The newActivation() method of the SingleInstanceListener of the first instance should be invoked. The second instance should exit without launching. This is the case if the jnlp_content is not set.
ACTUAL -
The second instance of the application shows the splash for some time before the splash is hidden. The second instance continues to load after the first instance has exited.

REPRODUCIBILITY :
This bug can be reproduced always.