Not working on Joomla 1.7

I have just set the component up on Joomla 1.5 sites, I setup the sub domains in Cpanel and set the document root to /public_html/, it worked perfectly, now when I tried doing the exact same process on my Joomla 1.7 site, it looks for pda.mysite.com, but it does not load the templates at all. Are there any other paramaters I should know about for Joomla 1.7, all the sites are on the same server, so I know it is not a server problem