I had nag-wear relating to this for a while whenever i was managing my site. It is now all that is displayed at the site url ie the site had 'died'!! I have over 5500 images stored and cannot access anything, more importantly neither can my visitors.

All I get is the following - is there a known cure or have i lost 12 months work??

The script template-functions.php has changed.
The script functions-filter.php has changed.
The script lib-auth.php has changed.
The script lib-utf8.php has changed.
The script functions.php has changed.
The script functions-basic.php has changed.
The script functions-controller.php has changed.
The script functions-image.php has changed.
Your server software has changed from Apache to Apache.
Zenphoto 1.4.4.1[596740f651] has been copied over 1.4.4.1[596740f651].
Your installation has moved from /home99a/sub005/sc62105-HHGW/www/wearwolfie to /home99a/sub005/sc62105-HHGW/www/wearwolfie.
Your database software has changed from MySQL 5.5.30 to MySQL 5.5.30.

Please reinstall the following setup files from the 1.4.4.1 [596740f651] release:

zp-core/setup/index.php
zp-core/setup/setup-functions.php
zp-core/setup/setup-option-defaults.php
zp-core/setup/setup-primitive.php
zp-core/setup/setup-sqlform.php
zp-core/setup/setup.css
zp-core/setup/setup_permissions_changer.php
zp-core/setup/setup_pluginOptions.php
zp-core/setup/setup_set-mod_rewrite.php
zp-core/setup/setup_themeOptions.php

The change detected is critical. You must run setup for your site to function.

Oh, and as a follow up I did reinstall the setup folder and run it and all I got was a load of database table creation warnings. I am still locked out of my own site.

The reason for this security measure is documented here:
http://www.zenphoto.org/news/installation-and-upgrading#re-running-and-re-uploading-setup-files
No, you would not loose any images by that.

1.4.4.1 is an older release and it got much more fine tuned in the current release.

Thank-you acrylian.

With some trepidation I upgraded the installation to the latest stable release using the link to the information you provided above - it turned out to be a breeze, apart from one or two deprecated functions for the particular theme I am using, and it was stress free and straightforward. Worked a charm - ZenPhoto remains a robust and great photo gallery/blog tool - thank-you so much for the easy to follow advice!! .