Umbraco 4.7.2 (using MySQL)

I try and copy a Home node using copy related (as I want to make translation).

I select Content as destination and select "Relate copied items to original". Once I click OK I get this error:

Server Error in '/' Application.

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Object reference not set to an instance of an object. 

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.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]

   umbraco.cms.businesslogic.relation.Relation.MakeNew(Int32 ParentId, Int32 ChildId, RelationType RelType, String Comment) +173

   umbraco.cms.businesslogic.web.Document.Copy(Int32 CopyTo, User u, Boolean RelateToOrignal) +2095

   umbraco.dialogs.moveOrCopy.HandleDocumentMoveOrCopy() +2250

   umbraco.dialogs.moveOrCopy.HandleMoveOrCopy(Object sender, EventArgs e) +74

   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118

   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112

   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10

   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13

   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36

   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563

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Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.272 

Doing a refresh I see that only the first node have been created but all child nodes have not.