Domain mapping isn't working (DNS is fine)

Hi,

No luck searching this so here goes... I've added domain mapping to my WPMU but it won't work, I just get the registration page each time. Here's the setup....

WPMU installed at journallocal.co.uk
Blog set up at f1kingdomcom.journallocal.co.uk
Domain mapping added for f1kingdom.com to point to f1kingdomcom.journallocal.co.uk
Nameservers point at mediatemple where my server is hosted
Media temple have the following A records...
- *f1kingdom.com A 72.47.237.126
- f1kingdom.com A 72.47.237.126
- http://www.f1kingdom.com A 72.47.237.126
Visiting f1kingdom.com simply takes me to http://journallocal.co.uk/wp-signup.php?new=f1kingdom.com where I'm invited to register (not reg is disabled for non-logged in users so only I see that)

I also added f1kingdom.com as an alias of journallocal.co.uk in Plesk but that changed nothing.

Any ideas why this isn't working, or how I might be able to find out?

Cheers,
Phil

P.s. for the forum admins - when writing a post, everytime I add a link with the toolbar it misses the closing A tag.