Paul Thurrott last week reported that some Windows Phone 7 users were seeing unexpectedly high levels of data usage. It's now being reported that Microsoft is investigating the issue.

The problem appears to be that some Windows Phone 7 handsets are sending large amounts of data, and opting to do so via 3G even in the presence of WiFi; the result is users burning through 2GB or more of data a month. Thurrott describes the issue as "curiously common," though it's certainly not universal. He has been tracking his data usage, but has no real explanation as to why it has increased with each month there's nothing obvious that's causing the data usage.