Domain mapping plugin not working

HI,

I've tried to get this plugin to work but to no avail. I followed all the configuration instruction but it doesn't seem to do anything.

I've got a subdomain install, the wildcard subdomain works, the account has its own dedicated IP.

What happens is when I go to site1.maindomain.com and try to map from it's wp-admin area the address to site.com and click on the map domain button, the circle thing appears, then nothing.

I checked in the database table wp_domain_mapping and there is nothing there.

Help?