Likely you are running version 7.21.04.00 of the KVM agent. If this is true there is actually no errors with the GUI. This version of the agent does not deliver out of the box dashboards, as also documented in the User's Guide manual:
"The Application Performance Dashboard in the Performance Management console does not contain a dashboard for the Linux KVM agent. You can view the attribute values of the Linux KVM agent by creating
custom charts and tables."
Hope this helps!