I have 3 cameras: 
Model RJ-3152 Hongkong R.J. Technology 
The all worked perfectly at first. Then one started showing a blank screen at dusk when it should switch to BW and IR. Now a second one is doing the same.  
The third camera is still working well. 
At dawn, all cameras come on and work fine until dusk when two show a 'video lost' image. 
The IR is on at night on all three. 
Any ideas what is causing the problem? 
I am running Geovision 8.3.