Caz,
Yes our DD did the same thing for a few weeks some months ago. it was driving me bananas. It was just when she was not getting enough attention from me and jsut as you siad, did not do it for DH or my mum or childcare - just me. It is so frustrating. She just stopped doing it. At first I went mad at her then I would just clean it up without saying anything and that seemed to work best.