Last night it got to the point where it just simply did not work at all anymore, so I had to look into it. Much to my surprise, the relevant article on the Apple Support Site, iOS: "Device not recognized in iTunes for Windows", actually helped. In my case, I had to remove and reinstall the Apple Mobile Device USB driver.
Reinstall the Apple Mobile Device Driver
- Right-click the Apple Mobile Device entry in Device Manager and choose Uninstall from the shortcut menu.
- When prompted, select the box "Delete the driver software for this device" and click OK.
- In the resulting dialog box, click OK.
- In the Device Manager window, right-click Universal Serial Bus controllers and choose Scan for hardware changes from the shortcut menu.
At this point, the Apple Mobile Device entry did not reappear. Checking in the "Computer" window - the one which has your drives listed - showed an "Apple iPhone" device. I found it in the Device Manager under "Portable Devices". I had to then update the software:
- Right-click the Apple iPhone, Apple iPad, or Apple iPod entry in Device Manager and choose Update Driver from the shortcut menu.
- Click "Browse my computer for driver software."
- Click "Let me pick from a list of device drivers on my computer."
- Click the Have Disk button. (If the Have Disk option is not present, choose a device category such as Mobile Phone or Storage Device if listed, and click next. The Have Disk button should then appear.)
- In the "Install from Disk" dialog, click the Browse button.
- Use this window to navigate to the following folder: C:\Program Files\Common Files\Apple\Mobile Device Support\Drivers.
- Double-click the "usbaapl" file. (This file will be called "usbaapl64" if you have a 64-bit version of Windows. If you don't see "usbaapl64" here, or if there is no Drivers folder, look in C:\Program Files (x86)\Common Files\Apple\Mobile Device Support\Drivers. instead).
- Click OK in the "Install from Disk" dialog.
- Click Next and finish the driver-installation steps. Open iTunes to verify that the device is recognized properly.
This worked - as soon as I clicked "next", the iPhone's screen lit up and it started synchronizing.
This was on Windows 7 64bit, do check the article for other versions and more detailed descriptions.