Table <Tablename> is set to read only, user doesn't have enough rights on this table.
You are logged into the database as a user that does not have the appropriate rights to view the table definition. For example, if you have only SELECT rights to a table and try to view the table definition, then this message appears.
Other ResourcesGRANT (Transact-SQL)
Permissions and Visual Database Tools (Visual Database Tools)
Help and InformationGetting SQL Server 2005 Assistance