domain mapping and multi domain cant log in to admin

I have a freash Plesk server set up and purchased the latest version of Domain Mapping and Multi Domains from you guys to set up a single wordpress installation to host multiple wordpress sites on.

Everything is set up right, and works great - but I am unable to log into the admin for any of the re-directed sites apart from the host site?

The sites work find but I just cant access the admin on any of them.

I am using this only and purely to host multiple wordpress sites on a single installation... have tried re-installing a few times and no joy.

Plesk is set up right with the wildcard redirects for the domains in vhosts, and I use Zerigo for my domains and so all sites also have wildcard redirects as well.

so all sites are tld ie

http://www.site1.com
http://www.site2.com
http://www.site3.com

all hosted on my main install

http://www.site.com

Help please!!!