I just got a USB based Trendnet KVM TK-209K.
When I boot up with my FreeBSD 8.2 machine active, everything is fine. When I switch away, I see these messages logged (which look fine)
ugen0.2: <ALCOR> at usbus0 (disconnected)
uhub7: at uhub0, port 2, addr 2 (disconnected)
ugen0.3: <Apple...