Here's what I did to fix it. Hopefully it will work for you too.
- Open the Computer Management panel
- Click on the Windows Start Circle
- Right click on "Computer"
- Select "Manage" (It will probably have a little shield next to it on the left side)
- Under "System Tools," click on "Device Manager"
- In the new list that shows up on the right, select the little triangle to the left of "Portable Storage"
- You should see your iPhone in there.
- Right click on your iPhone and select "Update Driver Software..."
- Select "Browse my computer for driver software"
- It should now be asking you for the location of the driver. Type this (without quotes): "C:\Program Files\Common Files\Apple\Mobile Device Support\Drivers"
- Select "Next" and accept all defaults if anything else comes up.
That should fix it for you. Let me know if you have a problem.