The /allusers switch is valid for Formativ Solution Installers but not the Framework products, such as Formativ Runtime.
As we have not yet had similar problem reports, there is no obvious reason why your settings in the formativconfig.txt are not working. I presume your formativconfig.txt file is in the same folder as the Runtime installer? Are any settings being changed by the config file?
Are you able to send a copy of the formativconfig.txt to email@example.com?
I suspect that the default Registry settings for Formativ Runtime should meet your requirements. The default setting should be the NetWare Client as the primary choice and if it is not available (it will be available in your case) it would default to LDAP.