I have been using a free version of angry birds on my LG phone for the past few months. I have completed 3 of the different sections but today when I look at it it says I have only done 8 out of 21 of the first level, none of the second, and of the third twelve out of 15. i'm pretty sure i'd done several of the 4th level too but that seems to have been wiped.

Any ideas what has happened and how I can fix it?

Thanks.