@wishpony
I modified the compatibility code between Polylang and Custom field template to enable compatibility between Polylang and another plugin (The Event Calendar).
I made some tests with the latest version of Custom field template (2.1.5) and it seems to work as expected.
If you want to test the modified version before the next official release, you can test the development version (1.1.1.3)
http://downloads.wordpress.org/plugin/polylang.zip