Billing page a bit wrong?

[#1]

Been at work all day (21st May), so far only checked emails and stats on my website.
Billing page says I've used nearly 700MB today. That's equivalent of a whole film on iPlayer!
edit -
no updates or anything. Don't allow auto updates.

[#2]

Hi,
I've just taken a look at an hourly breakdown of your usage and we've seen 673.5861MB downloaded and 12.4819MB uploaded between 4pm-5pm.
That's where a chunk of this appears to have come from. Is there anything you can think of that was used at that time?

[#3]

Hi Chris,
Something not right there.
Didn't get home from work until 6 pm yesterday (21st). Computer was off and ethernet cable unplugged all day. (Wireless is always off.)
Around 7 pm or so I checked email and stats on my website.
Didn't use any significant bandwidth till after 12am (22nd)
edit -
Just seen Linn's reply on the Feedback page. Seems there's a bug. No worries.