In order to keep your forms and source code synchronized, Delphi must be able to find and maintain the uses clause of each module. 

In a unit, a valid uses clause must be present immediately following the interface reserved word. In a program or library, a valid uses clause must be present immediately following the program or library header. 

This error occurs because the uses clause has been deleted, commented out, or incorrectly modified. Use undo to reverse your changes or correct the declaration manually.