This was reported by a developer on the OS X port mailing list. Similar to the change we made for applets, Java Web Start apps cannot open a file if its name has a non-Roman character. We need to add the LC_TYPE=UTF-8 workaround until JDK 8, where this bug is fixed.

I'll add a test case, but it's a simple matter of running an app in Web Start and showing a JFileChooser. Files with non-Roman characters will not be visible in the list, and can't be opened.