I've configured my Commerce site to use Asp.NET Identity and it all seems to be OK: I can create contacts, organizations etc and view all other Commerce content OK.

However, if I create a contact and then choose 'Create account' for the contact the 'Create Account' dialog appears correctly but when I fill in the detilas and click 'OK',

I get the following error: 

Server Error in '/' Application.

Default Membership Provider must be specified.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Configuration.Provider.ProviderException: Default Membership Provider must be specified.

Source Error:

Stack Trace:

[ProviderException: Default Membership Provider must be specified.]
   System.Web.Security.Membership.Initialize() +534
   Mediachase.Commerce.Security.SecurityContext.ValidateMembershipUserPassword(String password) +17
   Mediachase.Commerce.Manager.Apps.Customer.Modules.MembershipAccountEdit.UserPassword_ServerValidate(Object source, ServerValidateEventArgs args) +66
   System.Web.UI.WebControls.CustomValidator.OnServerValidate(String value) +173
   System.Web.UI.WebControls.BaseValidator.Validate() +134
   System.Web.UI.Page.Validate() +200
   System.Web.UI.HtmlControls.HtmlButton.RaisePostBackEvent(String eventArgument) +111
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1890

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.4001.0

I've seen this error mentioned in the forums in connection with the login page, but not with this dialog - any ideas anyone?