Hi; I updated my iTunes to the latest version (11.1.4.62), but it does not detect my iPhone 4s any more.

I find this on another post and tried it. It WORKED. I had to modify to fit my situation but give it a try. Good luck.

Go to Windows 8.1 Control Panel.

Go to Hardware and Sound; Devices and Printers; Device Manager; Portable Devices (look for Apple IPad)

Right-click, then select properties on the menu list.

Under the "Driver" tab menu, confirm the update driver button is not greyed out. If the update driver button is grey and unselectable, you need to select and click "Change Settings" button located near the lower left corner.

Now you can click the "Driver" tab menu near the top, so you can see the "Update Driver" button.

Select "Update Driver".

Select and click "Browse my computer for driver software".

For Windows 8.1 64 bit, it should be located in the folder: C:\Program Files\Common Files\Apple\Mobile Device Support\Drivers.

Click Next, and let the driver re-install.

iTunes 11.1.4.62 should open automatically if your iphone is connected already.