New Post: Manual Upgrade 4.1 -> 4.2

Now the exception have to be different, can you post it here?

Likely one of the classes in Composite.Generated.dll is referencing an old CultureName field, which is already removed from the database.
Are you using the old version of Composite.Generated.dll? Normally you can generate a new one when you restart/stop the website on IIS. If it isn't created - the error should be in the log files.

Also you can check meta data files, to see if IPageThemeSettings is constaining "CultureName" there for some reason:
/App_Data/Composite/DataMetaData/IPageThemeSettings*.xml