Can not Delete GW External Domain (gw6.5)

GW6.5
Was GW External domain: LTEST.
I need delete this Doamin.
I do as:
Run C1.
Connect to the Primary GW Domain.
Select domain LTEST.
Rigt Button on mouse.
Delete
Yes
And have error:
Deletion failed: System link exists (db48).

Whac can i do for resolver this problem ?

Serg