Opening SLN file skips the login dialog box

I have reinstalled a computer of a user and now he is having a problem with the Dimensions Plugin in Visual Studio 10

When he opens VS, selects File / Source Control / Open from source control, he is asked for his password and the plugin works fine.

But when he opens a SLN file, the plugin is only briefly visible, it doesn't ask for a password (dialog box disappears automatically again) and a message is displayed 'unable to access database'

When clicking change bindings I can see the connections, and if he click browse it works, but only until he closes the solution again.

Do I need to reconfigure the bindings or change a setting?

Sorry I’m not very familiar with Serena