I created a DotNetNuke (4.0.2) website using a starter kit.  I was able to run it, log in as admin and make some changes and everything works fine.  I used the default SQLExpress database for the project.  As soon as I attach to the database in SQL Sever Management Express, the website will not work.  Even though I did NOT change ANY of the settings in SQL Server Mangagement Express (I just wanted to check the security settings) I receive the dreaded

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 '(MyMachine)\ASPNET'.

To make sure that I wasn't missing anything, I created several sites and had the exact same results.  They all worked fine until I attached to them in SQL Server Management Express and then they all received the same error.  I actually created the original one just to make sure that DotNetNuke was working properly on my machine because I was receiving this error when I tried to copy  a DNN site that another developer had created onto my machine. 

When I googled this particular error message I actually came up with a huge lists of live sites that are returning this error!  Unfortunately I did not find any useful articles or posts about how to solve the problem.