Hi Patrick
following my article should resolve this. The MSSQL$SBSMONITORING and
MSSQL$SHAREPOINT instances are create by SBS and use MSDE. You need to create a new instance for BES to use. Follow the steps in the articleusing the SBS CD 3 files or download.

Chris Dalby Blog » Blog Archive » Installing MSDE on SBS for Blackberry Enterprise Server

Let me know how you get on
Chris Dalby