Java Web Start Applications cannot start from folders containing non-ASCII chara

FULL PRODUCT VERSION :
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) Client VM (build 14.0-b16, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows XP Processional Version 2002, Service Pack 2

EXTRA RELEVANT SYSTEM CONFIGURATION :
client is behind a proxy with NTLM authentication

A DESCRIPTION OF THE PROBLEM :
Webstart can not launch if a own JRE was installed with the ExtensionInstallerService into a user specific cache directory whereby the path contains non-ASCII characters.

The JRE gets installed successfully and the deployment properties in c:\Documents and Settings\<user name>\Application Data\Sun\Java\Deployment\ have a property like this:

deployment.user.cachedir=C\:\\Documents and Settings\\X9TFA\\My Documents\\1webstart\u00E4\u00F6\u00FC

the last directory path segment have german special characters and they are UTF encoded. The path was set via System Control->Java. The downloaded JRE is installed into ${deployment.user.cachedir}\6.0\ext\E12... If the user tries to start the application with the installed JRE an error messages occures (here in German):

"Fehlerhafte Installation. Fehler beim Aufruf von Java VM (SysExec)
C:\Documents and Settings\X9TFA\My Documents\1webstart\u00E4\u00F6\u00FC\6.0\ext\E12...\bin\javaw.exe"

The non-ASCII characters encoded in the userCacheDir path are not decoded before starting the VM. It doesn't matter whether the user name or some path segments containing non-ASCII characters.

This bug is known on Mac OS: http://devworld.apple.com/releasenotes/Java/Java104R6RN/ResolvedIssues/ResolvedIssues.html -> Radar #5078692



REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
not known if the client should be installed for user with non-ASCII characters in it's name