When paying off a planned gift and applying an over payment as a donation, the error, "Data could not be saved. The total amount must equal the sum of the designations", is thrown if the same designation is used for both applications and the constituent has a matching gift relationship.
We are currently evaluating this issue for a fix in a future service pack.
Steps to Duplicate
1) Set up matching gift conditions on an organization's Organization info tab. 2) Add a matching gift relationship between that organization and an individual that matches the above conditions. 3) Add a $50000 planned gift with the vehicle Living Trust for the individual constituent used in step 2. 4) Add the planned gift as revenue. 5) Go to the individual constituent's record and add a payment for $60,000. 6) Apply $50000 to the planned gift and the remaining $10000 as a donation to the same designation used on the planned gift. 7) Notice that you receive the error, "Data could not be saved. The total amount must equal the sum of the designations."