Incorrect Customer Balances

[James McDonald]

In Freeside 1.5Pre6, we have some customer accounts that are showing  
very strange balances. In the billing history, the latest invoice  
shows as Open with a balance equal to 2 months of service. When the  
invoice is viewed, however, it shows a $0 balance. The total balance  
in the billing history shows about 2 months worth of service  
outstanding, but if you go to the Post Credit or Post Payment screen,  
it again shows $0 balance. I've verified the charges and credits to  
the account and the account should show a $0 balance. Why is the  
total of the Balance column and the status of the last invoice not  
showing correctly?