I have this problem with a few of these NVR's during the day when a lot of recording is ongoing, I believed it to be at the time a network issue or the nvr's processor cannot handle the load of recording and administering at the same time. It is hit and miss with this issue. Once it starts, I cannot get access to any of the cameras. I usually just wait and will try it after hours and yes a reset will usually fix the issue. If it was a onvif issue in my case it should do it all the time but it does not do it all the time. These systems I remote in through the web gui. Sometimes if i push it it will lock me out and I will need to take a road trip to do a reset because I have lost all access to the administration side of the nvr. Its annoying as hell sometimes. I got called early this week to go on site because of police activity needed to see some video. The client was using smart pss and lost access to the admin side and this was on site. WTF, One thing I have noticed is that certain PC's that have lower specs will cause this issue hands down when using smart pss and the web gui. Not sure wats going on but When Im home at the mothership I have 3 of these and it has never happened. I think it might be buggy firmware that is reacting to a busy network or a slow computer on the client side. Another thing that creates this issue is when you are trying to view video, the nvr will hang and lock out the admin side. When I go on site and check the nvr, it is still recording fine but has for some reason frozen the admin side and a reboot will fix this, the log shows no errors other that the account is still logged on.