My friend bought one on a good deal. It worked well for a while, then the volume mechanism started acting funky. He would turn it up with remote or knob, and there would be a delay, then it would just crank up. Was horrible, he swapped it for an Onkyo
Try disconnecting everything, including the power from your wall/surge protector. Give it 30 sec. Restart receiver with nothing connected. See if problem persists. If it still persists, try to access the setup menu and quickly disable network features. I am not familiar with HK menus as I have...
What all do you have connected at the time it is doing this? Did you buy this from authorized dealer? Also, does the remote still function when you say the buttons lock up?