How to change opening balance back to zero

[CrimsonTide]

Not sure what happened, but when I look at Unpaid Accounts Report the balance doesn't match the invoice balance due. When I looked at the Opening Balance its an amount from a previous balance that was paid. Not sure why it doesn't zero out. I credited the account. And this only with just a few accounts. Read someone said to Recalculate, so I did that but it still shows an Opening Balance with an amount from a previous invoice. Thanks