I have an IPA signed for ad-hoc distribution. I can install it fine with Xcode Organizer by dragging it to the device. It also worked with iTunes <=10 by dragging onto th
open your iTunes "Side Bar" by going to View -> Show Side Bar
drag the mobileprovision and ipa files to your iTunes "Apps" under LIBRARY
Then click on your device.
open you device Apps from DEVICES and click install for the application and wait for iTunes to sync