Netware OES SP1 , Secure iPrint, iManager 2.5

We are currently running secure iPrint with Medium security selected on
all printer agents.
As per my recent posts I wanted to test the effect of changing the
security level to High. When I do this and then go back in to manage the
printer agent through iManager I get errors like this -

'Exception reading printer control '

For some of the printer agent tabs.

I am then forced to open nwadmin to change the security level back to
Medium and all works fine again in iManager.

All these tests were done with Admin and Admin has full ACL management
rights over the printer agents in the Access Control tab.

This occurs in the live system and various test systems.

Any ideas?