During upgrade to the K1000 6.4 the update does work.
On the console and in the update log the following can be found:
[Tue Aug 4 15:33:31 CEST 2015] [notice] Please consult the release notes if you wish to upgrade your appliance to an English-only version.
[Tue Aug 4 15:33:31 CEST 2015] [notice] The 6.4 release is ENGLISH ONLY. We have detected that non-English locales have been configured and the upgrade can not continue.
[Tue Aug 4 15:33:30 CEST 2015] [notice] kbox_upgrade:: Running kbox_upgrade.php part 1
The version 6.4 of the K1000 is English only.
See https://support.quest.com/kb/153537 for additional information.
A localized version is planned and will provided later.