I forgot to include the relevant part of /var/log/messages: Jun 18 18:24:12 george kernel: drivers/hid/usbhid/hid-core.c: can't reset device, 0000:00:1a.0-1.2.2.4/input0, status -71 Jun 18 18:24:12 george kernel: usb 1-1.2.2: clear tt 1 (00a0) error -71 Jun 18 18:24:12 george kernel: drivers/hid/usbhid/hid-core.c: can't reset device, 0000:00:1a.0-1.2.2.3/input0, status -71 Jun 18 18:24:12 george kernel: usb 1-1.2.2: USB disconnect, address 6 Jun 18 18:24:12 george kernel: usb 1-1.2.2.1: USB disconnect, address 7 Jun 18 18:24:12 george kernel: usb 1-1.2.2.2: USB disconnect, address 8 Jun 18 18:24:12 george kernel: usb 1-1.2.2.3: USB disconnect, address 9 Jun 18 18:24:17 george kernel: drivers/hid/usbhid/hid-core.c: can't reset device, 0000:00:1a.0-1.2.2.3/input1, status -110 Jun 18 18:24:17 george kernel: usb 1-1.2.2: clear tt 1 (0090) error -19 Jun 18 18:24:17 george kernel: usb 1-1.2.2.4: USB disconnect, address 10 After that the system is unresponsive and I have reboot with the power switch. Those devices are: Jun 18 14:47:40 george kernel: generic-usb 0003:04F2:0833.0002: input,hidraw1: USB HID v1.11 Keyboard [CHICONY USB Keyboard] on usb-0000:00:1a.0-1.2.2.3/input0 Jun 18 14:47:40 george kernel: generic-usb 0003:045E:0029.0004: input,hidraw3: USB HID v1.00 Mouse [Microsoft Microsoft IntelliMouse® Optical] on usb-0000:00:1a.0-1.2.2.4/input0 One last question, should I post text only to this list or are people happy with html formatting? Joe On 06/18/2012 07:42 PM, Joseph Areeda wrote: > Greeting, > > This is my first post to this list, I'm hoping for some insight into a > vexing problem. > > My situation is 4 computers running various operating systems: Ubuntu, > Scientific Linux 6.2, Debian Squeeze, MacOS X lion, and Windows 7. All > except the Mac and one Ubuntu are multiple boot and used for cross > platform development and testing. > > I have a manual switch box with computers on ports 1-4 and a powered > USB hub with mouse, keyboard, scanner, microphone and a USB headset > adapter. > > There is also an HDMI and DVI switch box but they are not part of of > the problem. Together they give me a more flexible KVM switch. I can > watch a long running job on Monitor #2 connected to one system while > working on another using Monitor #1. > > When I boot up everything works fine. I can also switch between > systems freely. However if I leave one of the Linux systems > disconnected for a long while it doesn't respond when I switch back to > it. I have not seen this behavior with Windows or Mac. The Mac is > sometimes disconnected for days but Windows usually gets booted back > into Linux when I'm done with it. > > SL6 usually dies but I can usually ssh into Ubuntu and reboot > cleanly. SL6 doesn't respond to pings or ssh. As long as I keep the > switch box on SL6 it has run for weeks. > > Now I have tried 2 different USB switch boxes and when it doesn't > respond it doesn't respond even if I plug the hub, or the mouse and > keyboard directly into the usb ports on the system. I don't believe it > has anything to do with the KVM the OP mentioned or my switch boxes. > > Searching the web I found a comment that said a powered hub per system > worked with his USB KVM switch. I suspect we're seeing some sort of > USB timeout. I suppose I can get a powered hub per system but I built > these machines with 6 or 10 USB 2 and 2 or 4 USB 3 ports so I really > don't need them. The powered hub may however convince Linux that there > is something plugged into that port and keep it alive. > > Does anyone know of a reason for this or even better a fix for it? > > Thanks > Joe