VMware Player & USB
While on the go, I use an HUAWEI Mobile Broadband E1692 HSDPA USB Stick for 3G connection.
After some time that I wasn't using it, it stopped working. No error messages, it just won't get recognized any more in the USB devices. Nothing at all, not even an unknown device, just as if it wasn't even plugged in.
After some fiddling I recalled that I had installed VMware Player. Just as I removed it, the USB stick returned to life.
Note that I wasn't using it in a VM, but directly on the host. And there weren't any VMs running nor the player itself running.
I suspect, as the player can redirect USB ports to the VMs, that some kind of USB device filter was installed by the player that prevented the USB stick to be seen by the host OS. It seems to have affected only that particular stick, as other USB devices were running as usual.