Ajax not working when installed in URL subdirectory

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I am running Concrete5 under nginx with php-fpm. I am running a number of sites in this configuration without problem. However i am trying to setup a concrete5 install inside a url subdirectory.

The install works fine but when entering edit mode, i cannot add or edit blocks. The URL for the Ajax request gives a "Failed to load resource: the server responded with a status of 404 (Not Found)" error, which results in the infinite loading icon.

My nginx config
location /documentation {
          root /home/objcloud/www/objcloud.com/docs;
          index index.php index.html index.htm;
          if (!-f $request_filename){
             set $rule_0 1$rule_0;
        }
        if (!-d $request_filename){
             set $rule_0 2$rule_0;
        }
        if ($rule_0 = "21"){
             rewrite ^/(.*)$ /documentation/index.php/$1 last;
        }
         location ~ \.php($|/) {
          try_files $uri =404;
          set  $script     $uri;


Regards, Frazer

frizzleb