I was having the same problem and did not want to re-install the plugin as I had created a long form. I did some digging and found a file called abspath.php in the /wp-content/plugins/cforms/ directory. If you edit/view that file, it contains the absolute path.
I was able to use that path and it works perfectly without re-installing or creating a new form. Try it out and let us know if you have different results.
