It seems Interlaced PNGs are not supported in ORx. Worse, the error message was a standard 'can't read the file or link it to a texture' message.
Preferrably, of course, ahve ORX support interlaced PNGs. However, at the least improve the information given when something goes wrong (Something like "The file was loaded OK, but the data seems to be corrupted")
Comments
At orx level we don't get any details, just that the image couldn't be loaded.
Not a big problem though; just had to go through every one of my art assets and re-save them as non-interlaced.
Now figuring out a good way to get this engine working in a way I like
On linux ImageMagick will do the trick, no idea for OS X as I'm staying away as much as I can from it.