Problem: SharePoint Designer Automatically switches to Contributor Mode!
Another day, when I was trying to open a SharePoint site in SharePoint Designer, it automatically opened in the contributor mode!
So I tried: Prompt for user name and password security settings in IE, then re-opened the SPD. Yes, It prompted me the user name and pass and opened in the SAME contributor mode, although I have FARM Admin & Site collection admin access rights.
Finally I found the solution:
To get around that, go to, SharePoint Designer’s Menu: Site >> Contributor Settings and then click on the Disable Contributor Settings button.
It worked like a charm! 🙂 In case, This doesn’t work for you then, Try adding your account in site owners group.