That's really interesting, because although I haven't bothered to upgrade I've been experimenting with various download monitors to get some meaningful reading on downloads, the trouble is they all seem to record broadcast traffic as well as your own download traffic. I haven't managed to get anyone to give me a definitive answer if this broadcast traffic counts towards your download.
Even when the Internet is not being used, there still is traffic being recorded because the network card is still connected to the ISP. I wonder if this is what you are seeing?
Since 21:20 hrs my net monitor says I've downloaded 2MB and I've only been on this site. It sits there at about 3 - 6KBit/s all the time when I'm doing nothing.