I have this setup: left side = windows 7 x64 PC. Right side Mac Air 2011. Monitor (Dell 2407WFP Ultra) in the middle with the VGA hooked up to windows, and DVI to the mac. And plugged into the monitor is my apple usb keyboard / mouse.
To switch computers, as I do about 20 times a day, I unplug the single usb lead that plugs into the usb hub on the monitor and plug that into a port on either the mac or the pc, and use the vga/dvi switch on the monitor. the mac recognises the keyboard, external hard drive, mouse and memory sticks that are hooked to the monitor in about 1 second; windows has to re-detect every device every time I switch back to it. This takes about 30 seconds, which is about what it takes to detect any usb device (on this machine or most others I've used, so that's "normal").
Off topic, but I have tried a number of KVM's (about 5 different brands/prices) and such and they have had a single consistency amongst them: they die after about a month. I guess I switch a LOT.
After going to sleep the last time, Windows now does not recognise anything plugged into the monitors hub. It does recognise the hub exists but can't find a driver
for it, even though it was happily using it this morning and again at lunchtime (it's evening now). I've long ago disabled just about any system-related thing that tries to update or patch. windows update is both disabled and blocked by mac address in my router for this pc, because it purpose these days just seems to be just slowly feck things up over time. nothing gets updated, patched or changed by a process. So an update or change to the driver or other usb-related system or the monitor usb driver or anything has not occurred, and I have confirmed that. virus/trojan scan of course, but I don't have to mention that since it's so obvious.
i've tried the usual power cycles of the pc and monitor (pulling the power at the wall). I've tried hooking up a vista pc to that side of the monitor and confirming that it's happy with the keyboard and memory sticks. the mac of course works and doesn't complain. the windows7 pc works fine with a spare keyboard cabled directly to the port where the monitor normally attaches - I'm using it now. so the obvious routes are answered - but windows just refuses to work with the device.
what are some of the steps to debugging why this is happening that I might have forgotten.