nwbc screen not coming after enhancement of data model

I have enhanced the data model MM with the help of this document

SAP How-To Guide: Extend MDG-M Data Model by a New Entity Type (ERP Table, Reuse Option)

http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/f0861081-88e4-2f10-13bf-d15b19fecf32?overridelayout=true

After enhancement , during testing the nwbc screen login page comes, once i login and go to create material option, it asks to enter the material  name and CR type. But after this step the screen does not show up. it gives a blank screen. Can anyone help me with this plz!