Solution: Carefully comb through the project and filter out all references. Remove the unwanted references and replace the ones remaining with the version you want. Ex. I had 188.8.131.5200-0 and 184.108.40.20600-0. I wanted the newer one as it came with .Net 3.5 which I was using to build the project. So I replaced all the 220.127.116.1100-0 with 18.104.22.16800-0. And the error was gone!!!