ITunes is not recognizing my iPhone?

It's an iPhone 4s if that matters. It's plugged in, *and* my computer even recognizes it. When I start up iTunes though, it doesn't notice that there's an iPhone 4s plugged in.
What's wrong, and what do I do to fix it?

I followed these instructions:
http://support.apple.com/.../kb/TS1538

And re-installed the "Apple Mobile Device USB Driver".

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's 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.