The WARN in the subject matter appears in ~/log/zimbra.log whenever I attempt to login to the administrative console. This is followed by an INFO informing me that 'authentication failed for admin'.
There were no errors during my install nor in the install log. I even re-installed to confirm that the password I was using was correct (it is one I regularly use for this type of exercise so therefore I am unlikely to have mistyped it). I am, incidentally, able to login to read mail as admin (i.e. http://localhost, not https://localhost:7071), so it seems as though th authentication is actually working.
As far as I know the version I downloaded (FC 4 binary) is no evaluation and as I downloaded it last night it is unlikely to have expired by now in any case.
Anybody able to prod me past this point. As you can imagine a groupware system with a single, unmanageable, account is not terrbily useful.