I updated the assemblies for the MongoCSharpDriver and FluentMongo but this broke the unit tests. FluentMongo had a dependency on version 1.3.1. I therefore removed the reference to FluentMongo and used the MongoCSharpDriver extension methods for chaining (no code change, just references) and it all works beautifully. Just thought I'd let you know in case someone else did the same. Great work btw and will let you know how my little project goes, if interested :) This has just saved me days of work. Thank you very much.