Confused about multidomains.

I have a wp 3.01 set up on a dedicated IP using subdomains with domain mapping working fine.

I currently have a VPS and two IP addresses. I use one IP address for WP and the other one has several domains sharing it (some successfully mapped to the WP installation).

I have tried to set up one of the domains (not one already mapped) on the shared IP address as a domain to be used by the multi-domain plugin. It has set up fine on the WP installation and I can set up a new blog within wp using the plugin but the domain itself does not work. I have setup a wildcard subdomain A record pointing to the WP IP address in Cpanel but newsubdomain.newwpmultidomain just points to the original domain and not the newly set up blog.

is it the case that I need to have another IP address for each multidomain or is there a way I can set things up using WHM / CPanel?

Feeling a little out of my depth on domain/ip stuff, but learning . . .

Many thanks for any pointers.