When you meet such error You should try to force ffmpeg to use only TCP connection - I believe that when switching from UDP to TCP ffmpeg tried to pause stream what may not be supported by IPCam like Edimax IC 3030 .
Here is pice of code:
AVDictionary *opts = 0;
av_dict_set(&opts, "rtsp_transport", "tcp", 0);
avformat_open_input( &FormatContext, path.c_str(), NULL, &opts )