Can't change user interface language setting back to "Use system language"

Description

Steps to reproduce

1. Create new Alloy site by using the EPiServer VS Extension.
2. Go to the site at EPiServer->My Settings.
3. Login with a Windows user.
4. Change Personal Language to specific language (e.g., Danish).
5. Change Personal Language back to "Use system language".

Expected Save change successfully
Actual Can't save change due to the error

Workaround: This is a bug in Microsoft ASP.NET Universal Providers. This only happens where there are no other items in the profile. So add at least one item to the profile, like assigning e-mail to a Windows user.

From log file:
2015-06-04 16:11:33,449 [25] ERROR EPiServer.UI.Edit.UserMembership: 20.1.1 Unexpected Membership Provider Error. This may be caused by invalid combination of Role and Membership providers.:
System.Data.Entity.Validation.DbEntityValidationException: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.
at System.Data.Entity.Internal.InternalContext.SaveChanges()
at System.Web.Providers.DefaultProfileProvider.SetPropertyValues(SettingsContext context, SettingsPropertyValueCollection collection)
at System.Configuration.SettingsBase.SaveCore()
at System.Configuration.SettingsBase.Save()
at System.Web.Profile.ProfileBase.SaveWithAssert()
at System.Web.Profile.ProfileBase.Save()
at EPiServer.UI.Edit.UserMembership.SaveButton_Click(Object sender, EventArgs e)