Switch the SACM or set top box off, switch the PC connection, re-start the STB/ SACM and reboot the PC. Should work fine. If no-one gets the link for RW's site before I find it I'll post it for you.
Have a read through this
http://homepage.ntlworld.com/robin.d...tips/swap.html
it gives more info on swapping PCs on the connection.
Welcome to the forum by the way