AppPortal kerberos authentication failed

Situation:

We publish a desktop for our users and on this desktop the users can start the AppPortal connector to access their applications. Publishing the apps through the Start Menu would have been an option, but our users like the connector, so we have chosen this way. The AppPortal connector is configured with the config.xml file on the web access server. The configuration is set to use Kerberos authentication (EnableKerberos = "1") to create a single sign on experience.

In the pilot farm, based on vWorkspace 7.2 MR1, this worked fine. In the new farm, based on vWorkspace 7.5, the users see this error when they start the AppPortal:

When we manually create a new connection to the farm and use explicit credentials, the logon is successful and the users get their applications.

We have tested various scenarios:

1. older AppPortal client 7.2MR1 on new 7.5 server farm --> same error
2. server from pilot farm upgraded to 7.5 --> same error
3. from new 7.5 server created a connection to the 7.2MR1 pilot farm, with Kerberos authentcation --> successful logon!

Our idea is that 7.5 broke something that was working fine in 7.2MR1...

Questions:

Is anyone using a setup with the AppPortal on a published desktop? On vWorkspace 7.5? Can you reproduce the error by selecting kerberos?

Regards,

Patrick