There seems to be an issue with using stored procedures in SubSonic that do not have any parameters.  As a work around to that bug (or feature)...  try this:

SubSonic.StoredProcedure sp = SPs.UspNoParamProc();
//Stored Procedure command Is Null... ensure command is created
string dummy = sp.Command.CommandSql;

rptList.DataSource = sp.GetReader();
rptList.DataBind();