Did you follow the installation instructions? They are a bit different than the pre 1.5.6x instructions. I suspect the errors are because you are not following the installation instructions.

Most importantly, after uploading the files, you need to log into your zen cart admin, or just click on the admin home link, and then install the flexible footer menu in admin--tools--flexible footer menu install. Then you will select the template and reset the sideboxes in the layoutboxes controller.

Thanks,

Anne