I use another PHP application (open2300 for a weatherstation, if you are interested you should try it!) and that is suffering a similar problem on SuSE10.3. So I'm pretty sure that it isn't a zoneminder config problem on my server, but a more general PHP problem.
I guess the learning point is that as things were working quite nicely on SuSE10.2, why did I have to meddle with it?

Has anyone got any ideas, please?
Thanks, Philip.