Hello,
The hotfix package is intended to be run from the Final release of version 6.0, not the Denver pre-release. First, you will need to upgrade the Denver pre-release version to the Final 6.0 version by downloading the package below. After you have upgrade your version, you can then apply the hotfix package accordingly.
The upgrade from Denver pre-release version to the Final version of Kentico
CMS 6 can be downloaded from here:
http://download.kentico.com/KenticoCMS_6_0_DenverToFinal.exe (25 MB)
Best Regards,
Edward Hillard