Saving changes is not permitted in SQL 2008 Management Studio?

I recently started using SQL Server 2008, at first it was really nice, but then I started getting a weird error every time I tried modifying a table.

"Saving changes is not permitted. The changes 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."