Sirius Satellite radio - using up a lot of bandwidth/Internet

I was looking at the usage logs for the Internet at a client today.  Nothing too specific, just a general 'Usage by IP' report.  I have one client who uses multiples on multiples of Internet compared to others.  Using numbers from this report, in the last month, his computer has downloaded 60 GB of data, compared to an office average of anywhere from 1 - 4 GB.  All of his usage is Port 80.  He uses the Sirius Satellite Radio player.

I have other people at this office who also listen to on-line radio, but their usage is nowhere near this user's.

Is there something special about Sirius radio?

A couple of other notes:
- I have double checked his PC, and there is nothing else going on (no spam viruses, etc.)
- we have a super Internet connection (10 MB up and down)

Any helpful insight would be appreciated.

Thanks,

TN