Might sound silly, but did you also give that user "Read" and "Write" permissions on the database when you made the user (I think, I can't find a screen in the DNP to change it but I know I saw it, might be only when you make the user).
I would just make a new user and give it all the permissions possible and see if it works. Not having Select Permission on the dbo schema is truely odd.
I am guessing you then restored the DB online with the SQL Express DB .bak file. If you want I will post the steps I've used in the past to do that.
-Wilson Gearld Mead III
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