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!! .