Well certainly taking Gary’s approach may solve many issues, but not yours and it would seem that Gary may not fully understand how to configure Quintum’s and work with them based on his frustration.
Your problem could be in that you may not have changed the IP address of the A800 in all the places needed. For example, in the config gksys, there is the border element that many times you set to the same IP as the unit itself. When working with a network of quintums you may also have other quintums have their border element set to one unit to create a master/slave network. I am betting that if you go through the entire config carefully, you may find a place where the old IP is and you simply change this to the new IP.