Hi Mark,
It appears you live in the same area of Nottingham as me! Basically it sounds like you have a USB timing issue which causes the pc to freeze, this can be down to low system resources or old usb controller drivers (generally happens on older PCs). Best bet is to try the ethernet which 9 time in 10 will completely fix the problem. If this is on the pc then you will just need to enable it in your device manager (accessing this varies slightly bethween the different operating systems) and swap the cables over (i.e remove usb cable and insert ethernet) and reboot your pc and cable modem in sequence.
Check the link for contact details if you need anything!
Gary
P.s Welcome to the site by the way