I am getting an exception in MindFusion.Diagramming.Layout.Layout. Call stack is as follows:

Message : An item with the same key has already been added.
Source : mscorlib
Stack Trace :
at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at A.c0274eaab5f8f7793cb60cb3ae87931c5..ctor(DiagramItemCollection c970a513ad6e4aa62c1308323d7044674)
at A.c47db0f87fd3fc192de20dcefa4519197.cfa69ddaad60e34fd23f7b99905993c8c(DiagramIte
mCollection c970a513ad6e4aa62c1308323d7044674)
at A.c47db0f87fd3fc192de20dcefa4519197..ctor(Diagram c6d288cf08ca4dd554843fd0d84cfbf6a)
at A.c8655dea47a21b8217d86475a4814eb8f.cd9275cfbfcacc12c6f53a710dff6837a()
at A.cefca3aead523fc7ceae17b64783b924b.cf8166aeaa8ecee698f484b861c931e7c(c210dd93cc
f2b4d1d04f8ae675e87487a cf56634778083fb0e568bf49d3515aec9, cc5a99f75cb9bda3e6a6f0bc303a37751 c88c61ebfdcfaee194c6d155d77745cd2)
at MindFusion.Diagramming.Layout.Layout.cf8166aeaa8ecee698f484b861c931e7c(c210dd93c
cf2b4d1d04f8ae675e87487a c52319c3bd0e78eaa102a3fa2daff1ce2, Diagram c6d288cf08ca4dd554843fd0d84cfbf6a, Boolean cd26c1a8c19b07a0ae6c5febd49df6d01, Boolean c1f7ccf5b7e2a427e7b0e879f25677ca8)
at MindFusion.Diagramming.Layout.TreeLayout.c11331ec940f4b80205644674193186b7(Diagr
am c6d288cf08ca4dd554843fd0d84cfbf6a, DiagramItemCollection c970a513ad6e4aa62c1308323d7044674)
at MindFusion.Diagramming.Layout.Layout.Arrange(Diagram diagram, DiagramItemCollection items)
at MindFusion.Diagramming.Layout.Layout.Arrange(Diagram diagram)

Any ideas what could have caused this?
DavidL

Yes, I seemed to have two copies of a link in the Links collection - not too sure why, but changing the code that deleted and re-created the link in question seems to have solved the problem.

Thanks for your help.