Cant login to db after I do a db backup in SQL Express

I have a working dnn site. I've created several modules and corresponding tables in the database and everything works great. Then, I open SQL Server Management Studio Express, attach to the database, backup the database, detach from the database and I can no longer run my site (error shown below which says I cannot login to db). I can open the database from Visual Studio and see my tables, but I cannot run the application. Rebooting doesn't help. I've even tried copying over the database with a prior copy. It still doesn't work. The only way I have found to reconnect to the database is to copy over the entire dotnetnuke install directory with a copy I made prior to the backup. Then it works again.

Anyone else had this behavior? How do I fix it?

Thanks

------ DB ERROR BELOW ------------

DotNetNuke Upgrade Error

The Assembly Version ( [ASSEMBLYVERSION] ) does not match the Database Version ( [DATABASEVERSION] )

ERROR: Could not connect to database.

Cannot open user default database. Login failed. Login failed for user 'PARAPRO1\ASPNET'.

You should post over at the DNN forums onwww.dotnetnuke.com, this isn't an uncommon event. You should always back up your DNN database from DNN, not an outside product. When you did the attach/detach, you changed the database credentials so DNN can't log in. They can be fixed, and I think there was a script posted to do this at the DNN site, but at least you'll get the correct changes there.

Jeff