I have the same problem when plugging in my iTouch (4th Gen) on a Win 7 Pro machine. I've tried it many times and rebooted, but always the same thing happens, which is that Windows detects the iTouch is connected, because the pop up window always pops up, but iTunes won't detect the iTouch. All of this happened after donig an iTunes update from v11.1.3.8 ro the latest version. The updated version did not work at all. Tons of people have been having problems with the latest iTunes upgrade on the forums. They recommended that I uninstall iTunes and reinstall. I tried that and it still wouldn't work, so luckily I had my old v11.1.3.8 of iTunes and used that to reinstall, since that was the version that worked fine before electing to do the upgrade. Now iTunes was working again, but the only problem now is that it won't detect my iTouch, so I can't sync. This latest iTunes update has caused me nothing but problems and I'm still fighting to get everything working again. If I had not upgraded iTunes, everything would have been fine.