In SQL Server 2008, you might have gotten this message when trying to change the columns in some tables, add columns or change nullity conditions. “Save is not permitted” tables have to be dropped and re-created. The only choice you have is to click cancel, or to choose to save the message to a text file, which is, i think, not very useful .
Here is the solution:
Tools -> Options -> Designers, and unchecked the option “Prevent saving changes that require table re-creation”.
Thanks for the tip. It worked!