I think I may have found the problem. 4 of the domains are held by a different company from the others. While most of the domains are all set up correctly (and pointing to the smae IP) these 4 are set up as domains on a different IP, and have a page set up with the following code:
<FRAMESET COLS='0,*' border=0>
<FRAME NAME='blank' border=0 marginwidth=0 marginheight=0 top=0 left=0 NORESIZE>
<FRAME NAME='redir' SRC="http://www.myrealdomain.com" marginwidth=0 marginheight=0 top=0 left=0 NORESIZE>
At least one of these domains is actually listed in alltheweb and we get some referals from that domain (so somebody somewhere is linking to it but I have no way of finding out who)
I'm sure this is causing the problem. But what's the best way to deal with it in time for this month's deep crawl? I can ask to have the domain moved to another registration company (will take ages), for the DNS servers to be changed (but they clearly don't do this as standard). What do you think? And should I name the dodgy registration company?
You are getting this becasue you must be using their "free redirection service" which is dodgy. The registrar doesn't matter, it's the fact that the're redirecting. The quickest thing would be to find someone who has a dns server, and then point your domain at those dns servers. Then the dns server points the domain to a server of your choice which will serve up a page.
Changing registrars can be tricky and involve sending stuff in the mail sometimes to the quickest thing is to change dns.