I was importing some data from Excel to SQL 2008 this morning and everything seems to work well and fine. I successfully imported the data but I forgot to define the proper data types which means I had imported a integer data into a varchar field, so I go ahead in editing the table properties and to my surprise I was prompted with this message.
I looked around the setting of SQL and Management Studio to see whether this can be changed, and it is really simple. To change this option, on the Tools menu go to Options, then Designers, and then click Table and Database Designers. Select or clear the Prevent saving changes that require the table to be re-created check box as shown below
Apparently this is a new feature in Management Studio (SQL2008) to prevent n00bs from doing some bad stuff in your DB.