A few days ago, iTunes went crazy on me with the black UI of death and I had to reboot to get it going. After then, every time I tried to Sync, it would get stuck – syncing for days if I let it. If I pulled the phone out, I had no pictures on my iPhone.
After trial and error through every conceivable sync option, I deduced that my iPod Photo Cache folder had somehow become corrupted. After going into my Pictures, viewing and deleting the hidden iPod Photo Cache folder on Windows (Tools|Folder Options|Show Hidden Files and Folders), everything works again.