FWIW, the z800 and z820 machines have very specific requirements as to which slots can be used for HDN and HDX cards. My own z820 ran HDN like a train and I have high praise for those machines. As for USB devices, it could be a current issue, so I wonder if a powered hub might help? Certainly, disabling Power Management on all USB ports is a required tweak that many miss doing at first. I also added a USB3 card to an open slot as the z820 is woefully short on ports
