itunes error -44134

I have recently signed up to audible.co.uk to download their spoken word books. You have to download an additional element into iTunes in order to get the books onto iTunes and then onto an iPod. Once the audible audio file has been downloaded you then need to put in your audible.co.uk username and password to confirm the final move from mere folder on the desktop to usable file on iTunes. However, the verification process ends with the ominous words "could not authorise this computer because an error occurred (-44134)".
audible.co.uk say that no connection is being made with their server, even though I am online, and thus this is a Mac issue.
Any ideas please?