 <p>It seems you use Default Connection Factory. Did you try define connection strings with datasource parameter and indication on .sdf file?</p> <pre><code>&lt;connectionStrings&gt; &lt;add name="ConnectionStringName" providerName="System.Data.SqlServerCe.4.0" connectionString="Data Source=|DataDirectory|\DatabaseFileName.sdf" /&gt; &lt;/connectionStrings&gt; </code></pre> <p>If it won't work, I've got one more idea. You're logging in by Windows Authentication. Maybe it's not possible to make two parallel connections via the same credentials? I'm not sure, but try to check other way than windows authentication. </p>