cmanvar

hi, i have 6 Bosch Flexidome IP Cameras and ONE DVR ( DiBos-8.5 ). it was configured before by some of our engineers before and it was functional as well. but somehow it stopped proper function and lost most of features. yesterday i visited the site and understood that all cameras added to the system is not showing any video other than a black screen. so i removed all cameras and added again but the result was same with an error message " Device Camera-2 connection faulty ". did anybody face this problems before ?? have you seen this errors before..?? please let me know how can we come out from this problems.. attached snapshots also.. Thanks, Anvar