The changes required after installing Magento patch SUPEE-9767 can be time-consuming. To save time, you may also run the scripts listed at https://gist.github.com/schmengler/c42acc607901a887ef86b4daa7a0445b. They do not work in every case, but they can still be useful.
SUPEE-9767 form key validation fix script
Need help implementing this solution, or still looking for a fix to your Magento problem? Get in touch and I will be happy to help with your project.