I need some help!

I have made SEVERAL black berry cobblers that usually turn out wonderfully, but the one I made tonight turned out horrible! I was wondering if there was something I might have done.

My recipe was ,

1 cup self rising flour

1 cup sugar

1 cup milk

mixed together for the batter,

poured into a hot dish with melted butter and then added the sweetened cooked black berries.

normally this turns out perfect fluffy bread topping, and the berries on teh bottom.

this time the batter stuck, stuck to the bottom and was thick like paste.

could the self rising flour have gone bad?

any ideas on what I possibly have done wrong would help.

Like I said I have made many many of these and it is the first time this has happened.

Help!