clark-
it's not that we don't want to help, it's just that we are all very busy (so please be patient with us). let me first state that the slimbox mods to effervescence were not done by the original author, so it may be that there is some incompatibility in there with zenpress/zenphoto/wordpress that may have been introduced.
is your error that you are getting from wordpress? that's what it seems to be like. can you point me to a page that I can view where you are getting the error above?
and if it is zenpress/wordpress related, changing your slimbox to thickbox in zenphoto's theme won't solve the issue, as zenpress/wordpress just "displays" images referenced via a zenphoto URL, and it would be the wordpress theme that would dictate what display (i.e. slimbox/thickbox) method would show the image.
Does that make sense?