Security :: Cannot Establish Connection To AspNetSqlProvider

I've created an ASP.Net 4.0 web application. It uses Forms Authentication. I have an ASPNETDB.mdf file in my App_Data folder courtesy of SQLEXPRESS. I have appropriate settings in my web.config for connection strings and providers (since I know it will be asked for:

<add name="ApplicationServices" connectionString="data source=.SQLEXPRESS;Integrated Security=SSPI;

AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true" providerName="System.Data.SqlClient"/>).

I have roles and users setup. I have been running this with absolutely no problems in both my dev environment (i.e. Cassini) and on a "production" (not really, but a machine that was published to). And the "production" machine still has no problems.

So, everything has been working perfectly fine until early this afternoon and all of a sudden it all stopped. The only things I did from when it worked until it stopped was: I connected to and checked in all my code to a TFS server (2010) and then I updated namespaces all around. I have not made any changes to my web.config since it worked, nor to the database. I'm really not sure what happened. Oh, and the "production" machine never got the namespace updates. But, it did get a publish immediately before I uploaded everything into TFS.

It started with me getting a login failure in my app. I know the login is correct (it still works on the published system). So, I went into the Website Admin Tool and clicked onProvider Configuration -> Select a single provider... -> Click on Test next to AspNetSqlProvider (only option). I get back an error: "Could not establish a connection to the database." So, this tells me that for some reason, it can't see my database. All my roles and users still show up though in Security.

Since these two actions, I have wiped out all my code locally and refreshed from the first changeset in TFS. Still no workie. I still get the "Could not establish..." in WAT. Every post I can find online keeps talking about connectionStrings and database configuration (i.e. aspnet_regsql). However, since this was just working with no issues, I'm pretty sure none of these are my problem. Especially since I refreshed my code to an earlier "working" state (prior to namespace changes) to no effect.

I am not yet at the point that I'm willing to wipe my database and start over. Again, because this was working before. I have noticed and read several posts by Sukumar Raju among others (including his blog posts, one here) and none of them helped or were quite related to my specific issue. Good information, but not what I needed.

I'm sure something went offline somewhere and I can't see it. I did check to make sure that the SQLEXPRESS services (including Browser, etc.) were started. Even restarted them to no avail. I'm sure it has to be something simple and I'm just missing it somewhere.