Error Message: Upgrade fails: IncompatibleRemoteServiceException after upgrade

WombatDialer uses a "fat client" model where the client - running in your browser - is a complex JavaScript application. If you update WombatDialer, it may be possible that your browser still caches the previous version of the application client, so you get an "IncompatibleRemoteServiceException" because the server detects the client is out of sync.
In order to fix this issue, just click the "refresh" button of your browser or clear the browser's cache.