"Either this image is too big or there is no image at all. Yeah."
I get this message when trying to post ANY image, reinstalled wakaba with bare minimum config.pl changes (passwords, sql db info) with the same results.
Sounds like some sort of Apache problem. That somewhat confused and non-informative message happens when the script is told there is an uploaded file, but it doesn't actually exist.
I have no idea what would cause it, though. Do you have some other script that accepts uploaded files that you could test?
Nuked the subdir and installed on another, works fine now. Probably something I changed somewhere that I'd never be able to find.