Error when adding a new button in PurchTable form (AX 2009)

Greetings!

I added a new menu item button in PurchTable form (in AX 2009). But now, when I open it, I receive the following error:

Object not initialized.

(C)\Classes\\visible

(C)\Forms\PurchTable\Methods\changeDesign_BR - line 4

(C)\Forms\PurchTable\Methods\init - line 84

(C)\Classes\SysSetupFormRun\init - line 3

The error occurs in the changeDesign_BR method in the following line:

element.control(control::Reference_DINumber).visible(false);

This error stops happening only when I delete the new button I created. And if I create (or duplicate) any kind of button, menu button, etc. this happens again.

Can anybody help me?

Best regards,

Luiz Bezerra