Problem with Studio 2015 use

Hello. I have installed and activated my Studio 2015 upgrade.
I activated it.
Then when lauching it for the first time, I got 2 error messages:
Failed to add window bar command extensions.
 Then "Exception with sld.enterprise2.Platform.Client.IdentityModel.IdentityInfoCache"
 
Then Studio just crashed.
I went on the SDLSolution Finder anddeleted 3 files, as recommended: BaseSettings.xml, Plugincache.xml and UserSettings.xml.

I started Studio 2015 again and encountered the same 2 error messages again...

I do not know what to do. Is there a way you could help me please?
Thanks
 
Delphine

PS: I use Windows 7 Family Premium SP1. 64 bits