[Plugin: Gravity Forms Custom Post Types] Fatal Error when activating

When I activate this plugin, I receive this message and I cannot access to form editing:
Fatal error: Allowed memory size of 35651584 bytes exhausted (tried to allocate 1245184 bytes) in /httpdocs/wp-content/plugins/gravityforms/form_detail.php on line 2234

I already set 256Mb (!) in wp-config… What can I do?

I downloaded the latest GF update.

thanks!

http://ww.wp.xz.cn/extend/plugins/gravity-forms-custom-post-types/