Bill complete, accounting document not cleared

Hi folks,

We incorrectly created a credit memo type G2 and then had to cancel it using it's cancellation document type S2. On cancelling, the document flow shows the billing status as completed for both the billing documents but the accounting documents of both show as not cleared...this is causing both of them to appear in the receivables, FBL5N when actually, they should have cancelled each other out...any clues what is causing this and how we can fix it?

Thanks a lot!