In this paper, we introduce a new adaptive cross-layer error control protocol (NAC) for reliable and efficient real-time multimedia streaming in Wireless Sensor Networks (WSN). The proposed protocol uses an adaptive Forward Error Correction (FEC) algorithm in the application layer, a dynamic hybrid FEC/ARQ method, and an Unequal Error Protection (UEP) mechanism in the wireless link layer. Moreover, it dynamically tunes the amount of erasure codes per group of packets based on mean absolute deviation of recently measured average round-trip times, and cross-layer information such as arrival of acknowledgment packets, network traffic load, and wireless channel state. In fact, by dynamically determining suitable redundancy for the source packet based on the packet loss rate in the hybrid FEC/ARQ error control algorithm in the wireless link layer, we achieve significant improvements over the existing error control schemes, while decreasing the number of retransmissions in ARQ mechanism. Our comprehensive simulations show that the proposed NAC protocol achieves better performance compared to the popular error control schemes in terms of energy efficiency, frame loss rate, frame Peak Signal-to-Noise Ratio (PSNR), and delay-constrained PSNR for real-time multimedia streaming over sensor networks.