When attempting to change a package revision for a Deployment Group within the Management Console, upon submitting the change you may receive the following error:
This error occurs if another user has submitted a change to the revision or package deployed to that deployment group whilst you are in the 'Packages' section of the same deployment group.
When you select Review and Submit you will be presented with the error. Selecting OK will refresh the page and you should now be able to make changes to the packages assigned and submit them. This behavior is most likely to occur if multiple users have access to the Management Console on different machines and are actively testing and deploying new configurations to the same deployment group.