Why won't my iPad sync photos ("not enough memory") when it's half empty?
I have had iTunes go off the deep end thinking there were far too many photos.

I have had luck with several tacks so I presume there are a few bugs - one of which you may have run into:


Take the device to another computer (or another iTunes library on a shell account) and let it sync and erase all photos on iOS. Taking it back to the main iTunes library which has the correct photos sometimes works. I presume the error was an accounting one on the iPad when this works.
Change photo sync to a simple folder with a jpeg or two, sync it, and then change back to the settings I prefer. (rarely works)
Rebuild the affected library in Aperture or iPhoto - this seems to force new data into the media browser so iTunes is forced to take a better look at the sizes for your albums and photos as organized.


Sorry I don't have a sure fire answer - but maybe you haven't tried all of these or it sparks an idea of something else you can try.