I have suffered this problem for many months without finding the solution, with a DCS-6113 and DNR-326 camera. "Verification error. Add camera anyway?"
I finally decided to buy a DNR-202L, thinking that the problem could come from DNR-326, since I can connect via web and remotely to the camera, but when I configuring the connection to the DNR-202L, I had the same problem.
Updated all firmware to the latest version in the camera and DNRs, all browsers updated to the latest version, fixed IPs in camera and DNR, antivirus and firewall uninstalled, all port open, and the problem persists.
After changing many settings in the camera, and too many hours of work, I found the problem:
the solution is to configure authentication as "BASIC" and not as "DIGEST" as suggested by the camera manual installation, for security reasons.
This is in: "System overview -> Network -> Port & Access Name Settings -> HTTP Authentication option..."
I do not understand how D-Link recommends the use of this parameter, "Digest" option, that does not work with their own DNR's.
NO FURTHER COMMENTS.....
P.D. apologize for my low level of English.