If you are on 2.3 or 2.3.1, there is an update bug. You can download the latest version of MoneyWell directly from our website and drag it to your Applications folder to replace the older version.
This update error was fixed in MoneyWell 2.3.2 and shouldn't be a problem in the future. If you purchased MoneyWell from the Mac App Store, this problem won't affect you. Simply use the Purchases tab to install a fresh copy of MoneyWell or the Updates tab to check for updates.