My screen is black or frozen, what can I attempt to do to fix this issue?

The first thing that you should attempt to do is hard reboot the DVR. On our PC based DVRs it is achieved by holding the power button down in the front until everything shuts off. After about 10 seconds hit this same power button to power on the DVR and everything should open on its own (Windows may prompt you to start Windows normally, use arrow keys on keyboard and enter to select option). On our Stand-Alone DVRs this can be achieved by pulling out the power cord on the back of the DVR.