Dissappearing achivements

[queeg]

I definately got the game completed in normal and the achivement for finding wally/waldo 20 times, (i remember because i was annoyed that the difficulties didn't stack) then i continued to play for a bit and managed to get friend to the stars (which is all the stars on normal difficultly), today i looked because i'm slowly going through the game on kids and both achievements have disappeared. This makes no sense as i've still got the friend to stars achievement, which is not possible to get without completing to game.
Anyone got any ideas how i fix this?

[The Pants Party]

http://www.xbox360achievements.org/f...d.php?t=199143

Try searching a bit before posting, this was the second thread listed in the forum...