Offering 50% of asking price on a foreclosure is too low. Before entertaining offers of that nature, the selling bank will first lower the asking price 10% or so to try to generate more interest. If the property is over priced, sometimes waiting is the only thing you can do. 10-15% below asking price is the range that has a shot at getting accepted.
I see you have posted this question quite some time ago, so hopefully the asking price has come down quite a bit by now.