iPhone cannot be synced

I received an error recently while trying to synch my iPhone. I searched the Internet and did not find a clear cut solution to fix it. I figured the problem out on my own and am posting the issue and resolution for future reference; in case anyone else has the same issue and happens to search for the solution.

Error:
This error occurs while in iTunes and attempting to sync your iPhone to new content:
"iPhone 'x' cannot be synced. The required file cannot be found."

Versions:
Mac OSX 10.6.2
iPhone 3G 3.1.2
iTunes 9.0.2
iPhoto 8.1.1

Root Cause:
Photos were not syncing from iPhoto to iPhone via iTunes properly because the "iPod Photo Cache" was either changed or corrupted.

In my case, I recently used CleanMyMac to free up some disk space and it deleted the iPod Photo Cache. Later, when I attempted to resync my iPhone; the photos on the iPhone did not match the photos in the iPod Photo Cache, causing the error.

Fix:

1. In iTunes, select options on the Photos tab to manually manage photos that synch to iPhone. (Select option to "select albums..." and include "no events")
   
2. Uncheck all photos (Albums, Events, Faces) and sync. The result will be a sync that removes all photos from the iPhone.
3. Next, follow these instructions from Apple to delete the "iPod Photo Cache".
4. Once complete, return to iTunes and select which photo albums/events/faces (or all) you want to sync to iPhone and sync.

The issue should now be resolved as iPhoto will create a new iPod Photo Cache and sync your photos without error. As always, back up your data before deleting or altering system configurations. Good luck!