Hi Carl94580345-0854,
Please check that you're following the association configuration file creation process outlined in this article:
You may be running into trouble because of the browser version in use by your end-users.
You can also try coping the .XML file under User\Preferences\File I set the file to be copied to C:\Windows and set the default association setting to reference the file locally. This has worked for me in the past.
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