windows mobile connectionstring issue

I have a Windows Mobile CE 5 application, running on top of a SQL Server CE database. I use an .xsd file as dataset schema. After some hard work, I managed to make it work and it's been working a while.

Now, I'm trying to add two columns to a table. I successfully added the columns in database file and changed the commands in TableAdapter. I didn't update the select queries as I didn't need to. When I tried to run a query I updated, it failed and complained about missing columns.

Below you can see the table. When I try to edit the Source, an error occurs.

Connection string not set - cannot get data design context

I couldn't find any connection string that works. What can I do to make it work?

I ended up installing Visual Studio Service Pack 1, but I was still facing some errors. For that, I started Visual Studio with /resetskippkgs in command.