Posted on 30 November 2012
We issued a release of GameMaker: Studio last week which, in a few cases, has resulted in sprites and background resources being overwritten.
To the best of our knowledge, most projects have survived unscathed due to GameMaker's automatic backup. Regardless, we're both humbled and embarrassed by this error.
It is very important that you update to release (1.1.710) or later which fixes the issue. Please take action to do this if you haven't already.
YoYo Games Team