An error message occurs when you try to save table chnages in SQL Server 2008 Management Studio:
Saving changes is not permitted. The changes that you have made require the following tables to be dropped and re-created. You have either made changes to a table that can't be re-created or enabled the option Prevent saving changes that require the table to be re-created.
This problem occurs when the Prevent saving changes that require the table re-creation option is enabled.
To disable it:
1) Open SQL Server Management Studio (SSMS).
2) On the Tools menu, click Options.
3) Click Designers.
4) Select or clear the Prevent saving changes that require the table re-creation check box, and then click OK.
Note that if you disable this option, you are not warned when you save the table that the changes that you made have changed the metadata structure of the table. In this case, data loss may occur when you save the table.
This is a bug from microsoft, more information here.