I have posted an update to Effervescence_Simpleviewer on the Trac. I have implemented paging of the thumbnails for Subalbums. This can be viewed at http://www.albums.sbillard.org/China%202007/.
The theme only pages the subalbum thumbs,not the image thumbs (which are handled in this case by Simpleviewer) so the hack is not universal.

So how (where) do we get the SVN version of Simpleviewer, so we can use this?

The SVN version is of Zenphoto. See the "Working with the Code Base" FAQ at http://www.zenphoto.org/trac/wiki/DeveloperReference

You can download the efferevescence_simpleviewer theme from the themes page of the WIKI http://www.zenphoto.org/trac/wiki/ZenphotoThemes

Wow - this is great. So cool that you worked out how to parse the xml to work with Flash.. Makes me wander what else can be done.
Thanks for sharing!

I didn' work out the flash. I adapted that from the simpleviewer theme by Michael Sleman modified by Benjamin Crulli. There are still some problems to be worked out. Some of the subalbum pages do not "flash" properly. I haven't figured out what the difference between ones that work and ones that don't. Except: if you don't have images in folders that have subalbums all works. If you do have images, sometimes it works and sometimes it does not.

Oh I see -well - yours caught my eye first - so thanks!

Today I have figured out how to work around the problem with the pages that didn't Flash correctly, so there is a new version posted. I've probably taken this theme as far as I can go. There are things I'd like to add, like better error handling for empty albums (that breaks page rendering) and better Subalbum administration, but I don't understand the code/workings of ZenPhoto well enough to accomplish these.

Full description of Effervescence+Simpleviewer is now on the WIKI.