Signed Custom Progress Application prompts 2 security warning dialogs

Launch 
 http://nicole1.sfbay.sun.com:8080/JavawsMustangIntegTest/custom_progress/custom_progress_signed.jnlp
Security Dialog will be displayed as expected.
Wait for sometime ,without clicking 'Run' in the security dialog
Another similar security dialog will be displayed.

Expected behavior:
There should be one security dialog 

This is reproducible on all platforms with JRE 6u18,6u19,6u20

There is no issue with unsigned applications as in 
http://nicole1.sfbay.sun.com:8080/JavawsMustangIntegTest/custom_progress/custom_progress.jnlp