Hi Sonja,
This is because the upgrade to 9.2A "fixed" a bug for manual check payments. From the release note:
For Manual Check Payments, the Maximum Payment for invoices was being ignored. The Current Balance was defaulted as the Payment Amount. If the Check date made it eligible, Discounts were calculated. Manual Checks now matches System Checks; the Payment amount is now limited to the Maximum Payment and Discounts are not calculated when the Maximum Payment is not equal to the Current Amount.
You can avoid the maximum payment control by going to the company profile>System Options tab and enabling the "Set Amt Payable to Inv. Balance" option.