Can no longer access DokuWiki

I installed DokuWiki yesterday on Ubuntu gutsy server. I set the permissions of the various data directories as indicated by the installer.  I then added a bunch of wiki pages and all was working fine.

Today when we started out server and go to http://ourserver I can see 2 directories, DokuWiki and dotProject. Clicking on the later works as expected. However when I click on DokuWiki I get:
The requested URL /dokuwiki/doku.php was not found on this server.

Looking at the permissions in /var/www I have:
drwxr-xr-x ; 7 www-data www-data 4096 2008-03-28 10:20 dokuwiki
drwxr-xr-x 15 www-data www-data 4096 2007-11-15 08:01 dotproject

I can navigate to all the pages (/var/www/dokuwiki/data/pages) on the command line from my machine over putty, but loading on the same machine via a web browser does not work. Any ideas what has happened?

Thanks, Tom.