Since Serial-over-LAN (SoL) uses first available COM port (usually 3, sometimes 4) - if a client computer has a device which also uses this COM port (e.g. card reader, infrared reader, printer, etc) - it will experience a COM port conflict.
The workaround is to edit the Device Manager properties of the conflicting device - move from COM3 to COM6, for example. This does not require a reboot. However - it must be performed one system at a time... which may be issue for banking, retail, medical, or other environments with mass numbers of systems in this situation.
Additional investigation with operating system providers and device manufacturers is underway to identify a better solution.
On a funny note - in one instance a customer had a USB to COM port connector. Ya gotta wonder - why not plug the device into the existing client computer USB ports?