Lofty - Apart from LiveUpdate, there is another way of downloading and updating your virus definitions. Go to
http://securityresponse.symantec.com....download.html and download them (the file is about 4.7Mb). Once you have downloaded them, doubleclick on the file and it will update your virus definitions.
I use this method quite often because I'm never quite sure that LiveUpdate has downloaded enough code while I'm logged on - I use dial-up and sometimes LiveUpdate can be very slow (site congestion I imagine).