My wife and I have decided that marriage does not fit into each others dreams anymore. We have been married for almost 3 years and Just got a notice that after filing I-751, the evidence submitted with the form was "insufficient". Our marriage and relationship started and continued in the utmost manner of good faith. Our decision for divorce was a mutual one. We plan on continuing friendship in good faith and she will always be part of our family. She has a life here, she works hard, pays taxes and wants to continue her life here. We both don't want her residency here, her life, stripped away.
I like your attitude. It appears to me that what is missing is proof, not genuineness. I suggest you contact a lawyer locally. They should be able to assist with finding items of proof that you may have overlooked.