I just upgraded to a Dell Optiplex GX620 mini-Tower. I have had the system up and running for about a week and have encountered problems connecting devices to the USB ports. Of interest is that I have two USB devices connected (printer and keyboard) and have not had problems with them except in once case I got an error message on boot up indicating my keyboard has failed. Rebooting seems to correct that problem. It appears that once the machine has been running for a couple of days the USB problems start except for the keyboard and printer which appear to work fine. Rebooting does not solve the USB issues. I have installed the up to date drivers with no USB resolution. Today I downpowered the machine only to restart it a few minutes later. On startup the USB ports work fine. It appears downpowering the machine down and subsequent startup from a downpowered condition appears to temporairly resolve the USB issue for a couple of days until the problem appears again. Any suggestions are appreciated.