Can not perform this operation. The file is no longer checked out or has been deleted.

Problem:
While working with files in SharePoint Designer 2010 or Word 2010 and you attempt to check in a document you receive the following error message:
Can not perform this operation. The file is no longer checked out or has been deleted.
The cause of this issue is you have connected SharePoint Designer 2010 to an Alias for the site (DNS CName) which has not been configured as an Alternate Access Mapping for the site (AAM).


Solution:
Connect SharePoint Designer 2010 to the host name while performing these file operations. Not ideal but will work.
Or better:
Add the DNS alias to the Alternate Access Mappings in Central Administration. This will require access to central administration.

Access denied. You do not have permission to access this content

You have created an External Content Type in SharePoint Designer 2010 with the authentication mode "User's Identity". When you create a list and want to access the data in your portal, you get the error message "Access denied. You do not have permission to access this content" or "Access denied by Business Data Connectivity".

You need to set permissions in Central Administration under "Manage Service Applications" in the "Business Data Connectivity Service Application". Click the BCS service and configure the permissions in the context menu of your ETC.

Also the user needs permissions in your external database.