Hi,
I don't normally like to piggyback old threads, but I have the same issue.
vCenter 4.1 (no U1 as yet) and I cannot add Endpoint or CapacityIQ licenses to ours.
Diagnostic error seems to be rubbish as it displays all of the licenses I do have quite happily.
It must have worked in the past as we have added licenses okay.
TIA Rob.