Lazertech

Hi there people, im new on the forum. Iam from Argentina, iam a noob CCTV installer, and this is my first NVR system. I've a Qihan NVR 8 ch, with only one port LAN, and 8 Cameras Qihan 2mp Full HD. For the moment, ive isntalled 2 cameras, i bought a Switch 16 with 16 channels, 8 for the cameras, 1 for the NVR and 1 for the Router to give internet. The 2 cameras already instaled work nice (a little delay on the images but its cool) the problem is, when i double click in Channel 1, the image goes, and all i see is black. Like if the Camera lost the image... and that happen with all the channels, any idea? Can be the UTP cat5 cable? any conection? Its weird, i can see them in groups but no one by one in full screen :/ Im sure im doing something wrong, but i dont know what! Cameras uses port 5000, and ive changed IP to 192.168.1.100 -102 -103 etcetera... Should i open the 5000 port in switch? i think no... please help me! Or correct me if im doing something wrong! :/ When i try to see the records, i see all black because it shows 1 camera at time maximized, so i cant do anything.. Thanks all, hope u understand my bad english!