Record Renewal Payment - NaN(Not a Number).

When a renewal is being recorded for a renewal payment of over $1000, the field is populated with a NaN. I believe this stems from the way that membership minimum fees are recorded. When the min fee is entered through the GUI it is automatically changed to this format: $2,750.00 with the comma after the number 2. When trying to renew a membership that has a minimum fee like this, the field is briefly filled with the correct data ($2,750.00) and the quickly changes to read NaN. I have repeated this behaviour on the demo site for 4.1.