cannot close production orders

Hi guys,

When the user tries to close a production order in CO02 , they get an error which says the the purchase order still exists. but as i see in the purchae order , the delivery completed indicator is set.( one thing I can see is : in the invoice tab of item details final invoice indicator is not set) .Does the final invoice indicator has any effect on closing the production order?Please help me .I'd appreciate your help.

Thanks

Cheris T