HDFC has offlate changed the guidelines for 3rd party transfer and now one need to visit the branch and deposit photo id along with address proof for activation of the 3rd party transfer. This change in policy has been activated wef 13 Sep 2011.
So, if you have been able to transfer funds through third party, now you will not be able to do so due to change in the policy and for that you need to visit nearest HDFC bank or call their customer service. For details one can speak to the HDFC bank customer care at 09957193333.