When I run Zimbra Desktop it fails to run and gives an error:

Couldn't access Zimbra Desktop server. If issue persists after reinstall, please check logs for errors and report to Zimbra Desktop.

I have checked the logs and there is nothing there. I have tried re-installing from a new download and exactly the same thing happens. It was running fine yesterday but I cannot recall exactly when it stopped working.

Advice welcome as I do not want to lose my mail history, contacts or diary.