Tanner12oz is correct, at least in the eyes of those who are selling. They are selling because they are loosing faith in MB to deliver in the next few weeks, and feel it will take him another 3-6 months or more to file and are deciding to go elsewhere for a while.
Long Term, this is still a good investment, as I believe MB will eventually file - there is no reason not to, and every reason to get it done right.
If your here for the long run, then you don't have to much to worry about yet... The stock will continue to drop until a permit is filed or other substantial JV news is released.