FindComponent question

This works on a form:

  TLabel(FindComponent('Label1')).Caption:='It worked';

This does NOT work on a QR:

  TQrLabel(FindComponent('QrLabel1')).Caption:='It worked';

Access violation at address 00403B33 in module 'AIA.EXE'.  Read of
address FFFFFFFF.

Can anybody explain what is happening?  Thanks for all help.