I'm using Umbraco 4.7.1 and want to create a new member from within my code.

on the trigger of an event I am calling the Membership.CreateUser with valid parameters

Membership.CreateUser(userName, password, email);

but the function generates a Null refererece exception further down the stack.

[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.cms.businesslogic.Content.CreateContent(ContentType ct) +130
   umbraco.cms.businesslogic.member.Member.MakeNew(String Name, String LoginName, String Email, MemberType mbt, User u) +676
   umbraco.cms.businesslogic.member.Member.MakeNew(String Name, String Email, MemberType mbt, User u) +35
   umbraco.providers.members.UmbracoMembershipProvider.CreateUser(String username, String password, String email, String passwordQuestion, String passwordAnswer, Boolean isApproved, Object providerUserKey, MembershipCreateStatus& status) +122
   System.Web.Security.Membership.CreateUser(String username, String password, String email, String passwordQuestion, String passwordAnswer, Boolean isApproved, Object providerUserKey, MembershipCreateStatus& status) +444
   System.Web.Security.Membership.CreateUser(String username, String password, String email) +53
   GFO.MemberHelper.CreateNewMember(String userName, String password, String email, String firstName, String lastName) +659
   GFO.TeaCommerceEvents.WebshopEvents_BeforeMailSend(Order arg1, MailMessage arg2, EmailTemplate arg3) +634
   TeaCommerce.Data.EmailTemplate.Send(Order order, EmailTemplateType emailTemplateType) +1152
   TeaCommerce.Admin.Umbraco.plugins.TeaCommerce.Orders.EditOrder.BtnSendEmail_Click(Object sender, EventArgs e) +181
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +154
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3707

What would be causing this?

Thanks,

Matt