Problem following NIS update?

Since a new Norton update/new version(?) was downloaded to my laptop a week ago every time I use my Mobile Broadband dongle something is eating up the data usage at an alarming rate. As soon as I connect to the internet, even before I open an internet page, the usage starts clocking up. Could it be Norton that's using this up in background tasks or whatever? I know very little about this kind of stuff, any help would be appreciated.