FULL PRODUCT VERSION :
java version "1.6.0"
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
I get the following exception thrown whenever webstart updates a locally cached .jnlp file:

CouldNotLoadArgumentException[ Could not load file/URL specified: C:\Documents and Settings\keith\Application Data\Sun\Java\Deployment\cache\6.0\49\7c1f76b1-7a84d732]
	at com.sun.javaws.Main.launchApp(Unknown Source)
	at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
	at com.sun.javaws.Main$1.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

The wrapped exception is:

java.io.FileNotFoundException: C:\Documents and Settings\keith\Application Data\Sun\Java\Deployment\cache\6.0\49\7c1f76b1-7a84d732 (The system cannot find the file specified)
	at java.io.FileInputStream.open(Native Method)
	at java.io.FileInputStream.<init>(Unknown Source)
	at java.io.FileInputStream.<init>(Unknown Source)
	at com.sun.javaws.jnl.LaunchDescFactory.buildDescriptor(Unknown Source)
	at com.sun.javaws.Main.launchApp(Unknown Source)
	at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
	at com.sun.javaws.Main$1.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)


The file name specified existed before the application was launched.  However, by the time the exception is thrown, it has been deleted and replaced by a newer version with a different name.

This sounds like bug #6446676, which was supposedly fixed in Mustang(b94).  However, I'm still seeing it in b105.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
This happens every time a new copy of a locally cached .jnlp file is downloaded to the client.  Since we're dynamically building the .jnlp file on the server, this happens every time (other than the 1st time) the application is launched.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I expect webstart to use the new file that it just saved rather than the old file it just deleted.
ACTUAL -
Webstart throws the exception on every invocation after the first one.
Even though our application requires 1.5, our customers are starting to see this error as soon as they install 1.6 on their desktop since the newly installed 1.6 will handle the initial .jnlp file.

So, simply installing 1.6 on a client breaks existing 1.5 production applications.


ERROR MESSAGES/STACK TRACES THAT OCCUR :
Dialog stating "Application Error" "Unable to launch the application" with the previously mentioned exceptions.

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Either: (1) uninstall 1.6 so that 1.5 handles the ,jnlp file; (2) manually run the application in offline mode; or (3) delete it locally before launching.

Since our customers are accustomed to clicking a link on a web page to launch our application, neither of workarounds (2) or (3) is going over very well.

Release Regression From : 5.0
The above release value was the last known release where this 
bug was not reproducible. Since then there has been a regression.