Smart Grid (SG) technology aims at bringing the world's aging electric grids into the twenty first century. To this end, the current power grids require to be overlayed with a robust communications system. Home Area Network (HAN) is an important part of the SG communications framework through which the end-users are able to communicate with the electricity provider. In a HAN, there is typically a smart-meter and a number of electric appliances. Most of the proposals to-date have agreed upon using IEEE 802.15.4 wireless technology dubbed as ZigBee for the HAN communications amongst the smart meter and the various electric appliances. Although ZigBee provides few security features, the technology still suffers from a number of security vulnerabilities, particularly in case of SG HAN. In this paper, we describe a HANIdentifier (HANId) conflict attack against ZigBee for HAN communications and demonstrate the impact of the attack on SG communications through computer simulations. Finally, we also envision an appropriate framework to prevent the attack.