How do I make iTunes sync automatically when an iPhone, iPad or iPod is connected? When iTunes is already running and I plug in my iPhone or iPad, the device appears correctly in iTunes but it doesn't sync automatically. I'm sure it always used to sync automatically on connection, but now I need to start the sync manually (i.e. by selecting the device and clicking the Sync button). Does anyone know how I can get it to sync automatically as soon as the device is connected?

My details are as follows:


iTunes 10.5.1.42 on Windows 7 64-bit
iPhone 4 and iPad 2, both with iOS 5.0.1
iTunes > Preferences > Devices > "Prevent iPods, iPhones and iPads from syncing automatically" is unchecked.
For both devices, the iTunes setting "Open iTunes when this iPhone/iPad is connected" is unchecked.
I'm syncing via a USB cable. (I did try Wi-Fi sync but iTunes hardly ever found the devices so I disabled it on both iPhone and iPad. This may have been around the time auto-sync stopped working too but I can't be sure.)
I don't use iCloud for sync or backup.
It's the same laptop and library I've always synced against (so this answer doesn't seem to be relevant in my case)
iTunesHelper.exe and iPodService.exe are both running normally.
Your list holds the answer, specifically #4. The problem is the fact that when iTunes it prevented from automatically opening when a device is connected, there's a whole list of actions that simply don't happen, sync triggering is one of them.

Re-enable 'Open iTunes when this iPhone/iPad is connected' and your syncs should work normally, and automatically, again.