magento 1.4, nginx, php fastcgi through spawn-fcgi, and malfunctioning AJAX

[t3hslr]

Hi, 

Here is a screen cast of the issue:
http://screencast.com/t/ZquL9DBgvxmU

A Magento 1.4 site I administer was ported from Plesk+Apache to
cPanel+Nginx recently, and all seemed fine, except, the Catalog > Manage
Categories page has a lot of categories. The issue persists through both
the latest stable Firefox and the Google Chrome browsers. 

Once the categories are made, editing them on the web interface seems
impossible. AJAX [i]seems[/i] to run fine, since I get the "Please wait"
icon, but if I click a category, I cannot edit it because it doesn't
load from the left pane onto the editing pane(s). 

This thread on Magento's site details the same issue:
http://www.magentocommerce.com/boards/viewthread/200317/#t254131

Magento config: 

[code]
location / {
    index index.php;
    try_files $uri $uri/ /index.php?q=$uri&$args;
}
location /skin/m/ {
    rewrite ^/skin/m/([0-9]+)(/.*\.(js|css))$
/lib/minify/m.php?f=$2&d=$1 last;
}
[/code]

Note sure that skins part is necessary; saw it on another site and used
it. I'm running Nginx 0.8.53, also have and open_basedir and APC entry
in the PHP section, and fastcgi_pass is using PHP 5.2.14 running through
spawn-fcgi.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,150053,150053#msg-150053