Windows Phone 7 WiFi/3G bug

It looks like not all is fine and dandy at the Windows Phone 7 camp. Apparently users have been experiencing high data consumption on their devices despite not running anything. The worst part is, even if they are on a WiFi connection, the phone still uses 3G data instead – which is a headache for people who don’t have an unlimited plan. Nobody knows what the problem is right now and it isn’t a widespread issue, so the problem could be due to a buggy third party app but Microsoft are looking into it. Are any of you experiencing such problems? If you are, what do you think it could be?