Project costing - budget integration

We are specifying our budgetary control in oracle project costing as follows:

Budget type: approved cost budget

Control flag: yes

balance type: Encumbrance

Non-Project Budget: General Ledger Funding Budget

Levels

Project: Absolute

Task: Absolute

Resource groups: none

Resources: none     

Time phase

Amount type: Project to date

Boundary code: Project

When we come to save our record an error message appears saying : APP-PA-231495: Multiple integration to either the contract commitment or the General Ledger is not allowed.

We have checked no other windows are open.  We are trying to understand how the top down and bottom up integrations feed the general ledger.  However we cannot get past this error message to test.