Can't access dashboard for new sub-site


I have created a new subsite of a multisite install, the Startup Map, at :

This will be mapped to, for which I have already pointed the DNS.

My problem is that I cannot access the dashboard or log in. When I click on these options it just returns me to

One potential contributing issue is that I used to have a dedicated wordpress at this URL, and had the domain assigned at the web hosting company to point to this. I have de-assigned it, changed the DNS etc., but I don't know if that is still contributing to the issue..

thanks, Neil.