linq how to debug selecting objects into new objects

Hi,
I have a ton of xml web service responses which were converted into classes.  There are a few issues with these as we are seeing.  I commonly do something like the following to display some classes in a grid.  Sometimes depending on the input, everything blows up "Object reference not set to an instance of an object.".  When this happens, how can i go about trying to debug this?  I am guessing there is a null value or something.  I am looking for something reusable.

Thanks!


                var results = (from os in orderStatus.orderstatus
                               select new
                               {
                                   orderNumber = os.orderNumber,
                                   reportedTime = os.reportedTime,
                                   orderstring = os.orderstring,
                                   symbol = os.order.symbol,
                                   quantity = os.order.quantity,
                               }).ToList();