iPhone 4 not showing up in iTunes

I've had a Verizon iPhone since February, and haven't experienced any problems with syncing to iTunes (except wifi sync), but all of the sudden even when I plug in my phone over usb, iTunes won't recognize it.

This first happened today after I reinstalled iTunes to try to fix wifi sync. It fixed it for my iPad 2, which had previously only been able to sync over usb cable, but now my iPhone won't sync at all because iTunes doesn't even detect that it's plugged in. I tried different usb cables, and the iPhone charges when plugged in, so it's not a fault in the cable. I can still import pictures to my computer too.

I tried restarting my computer, restarting my iPhone, taking it out and plugging it back in. It seems like it must be something wrong in my iPhone, as my iPad will still connect and sync over both wifi and usb.

I'm running on Windows 7 x64.

I realized that when I plug in my iPhone, iTunes comes up, so it must detect something. But still the only device in my devices list is my iPad (which isn't plugged in, just over wifi).

It must detect I've plugged in an iDevice to pull up iTunes, yet it still doesn't show up in iTunes...