I have a site currently live at ssaib.uk.com but when you try and access the site at www.ssaib.uk.com you get nothing. It is not down to domain propagation and I have no idea why it is doing it. I've read mention it could be a conflict between xcache and eaccelerator however I have turned eaccelerator off without result. Any ideas would be greatly appreciated
This is due to DNS settings. You need a record for the domain WITHOUT www., usually represented in your domain management panel as an @ or blank or *.
If the DNS is resolving but the website isn't showing up, it could be that the web server is configured only to respond to certain hostnames - Apache for example has "virtual hosts" with different document roots, for example one could respond to "example.com" and another to "somesite.com" even though they resolve to the same IP.
Have a look in your web server settings.