MGC keybd loses connection WIN2K

On several new Win2K computers equipped with MGC keyboards and mice, the connection freezes leaving keyboards and mice frozen. Upon start up, keyboard does not respond to control, alt, del. If I hold right Shift key for 8 seconds, it will allow entry. We haven’t changed any settings to ask for features and cannot figure out how to resolve the problem. Extenders that worked well on other computers are in use. Units came with PS/2 drivers pre-installed. Any ideas as to why the input devices are losing the connections? And what else can I try beyond the usual troubleshooting suggestions in Win2K? Thanks.