The error you are encountering in the Stepwise platform indicates that there is complete or quasi-complete separation. This is a phenomenon that can occur for binary responses, when one predictor (or a combination of predictors) can perfectly predict the outcome. In this case the maximum likelihood estimates don't exist. There is a SAS note that addresses this issue with logistic models on our website at http://support.sas.com/kb/22/599.html. Although the note addresses SAS, the concepts discussed there are applicable to any software.