Try using Comparability View in IE, add IP address to trusted Sites, and make sure in security settings that "Download unsigned ActiveX controls" is set to Prompt for the Trusted Sites zone.
You should be able to use a USB hub at the DVR and connect multiple mice. I have done it successfully with several different dvrs. You can then use extenders for each mouse back to the usb hub at the dvr.. Use a powered hub to be safe so you don't overload the DVR's usb port.
out of range is usually the message from your monitor when the output resolution is greater than your monitor can handle. Try a different monitor and see if that makes any difference.