I'm not sure which cams you have or what your IpCamViewer setup looks like, but I think I had a similar problem with my new 4MP Hikvision. I solved it by changing the channel number (Ch.#) in IpCamViewer for the 4MP camera. I changed from channel 1 to channel 2. The problem camera was a 2T42WD-I8 4MP EXIR IP Bullet.