Store Proc execution gives error

I am trying to execute the store procSo under dataset properties I select commandtype : Store Procenter the SP name usp_rpt_Solution and press ! it gives me two parameters which I enter the values, but after displaying the results I get an error : Nullable Object must have a value.... Don't know what should I be looking for. Also , don't see the the fields populating in the dataset as they usually do after execution....