Hi! My father has a similar problem.
Anyone else with this problem notice an irregular data usage also?
My father S2 suddenly begun to use about 20-30 MB per hour (he normally use about 200 per MONTH!). Also the battery lasting halve of the time. Whatever is using the data, it also draining the battery?
Check this for more details:
http://androidforums.com/android-lounge/586589-samsung-galaxy-s2-became-data-hog.html#post4697753