Cannot login to site after 3.2 update

I receive the following error messages when I try to login to the admin on my site ever since I attempted to update to 3.2.

Warning: require(/home/icarlsba/public_html/wp-includes/class-json.php) [function.require]: failed to open stream: No such file or directory in /home/icarlsba/public_html/wp-content/plugins/admin-menu-editor/includes/shadow_plugin_framework.php on line 21

Fatal error: require() [function.require]: Failed opening required ‘/home/icarlsba/public_html/wp-includes/class-json.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/icarlsba/public_html/wp-content/plugins/admin-menu-editor/includes/shadow_plugin_framework.php on line 21

I have searched the forum for a way to fix the problem but I’m afraid I am not techie enough to understand. Any help you could give me would be appreciated. Thank you.