H9 works well with iOS in my iPhone 4, but, there are connection problems via USB in windows 7. I'm using other devices via USB (Digitech Jamman, etc) without any problem.
The H9 should work fine via USB on Windows 7. I've used it myself on Windows 7 with USB frequently without any problems. There are a couple of possible sources of problems.
(1) We have heard from users who had trouble communicating with the H9 via USB when using other USB audio devices. They discovered when they disconnected all of their other USB audio devices the problem disappeared. And I can remember at least one user who found there was a specific driver for an audio interface he had that was causing the problem.
(2) We have heard from users who are using a DAW at the same time as H9 Control on their computers. A DAW can try to capture all of the MIDI ports and may send MIDI messages like MIDI clock to all of the connected MIDI ports even if you didn't ask it to do so, and this can cause problems as the messages sent by the DAW interrupt the messages sent by H9 Control.
(3) It is possible that there is a hardware fault with the H9's USB port. They have been known to come lose from the board if a USB cable is inserted with too much force into the port.
If you've eliminated (1) and (2) as possible sources of problems and you think you're H9 might have a hardware fault, you can contact firstname.lastname@example.org if you'd like to arrange to send it in to us to look at. Alternatively, you can also connect to your H9 from Windows with a Bluetooth dongle. This FAQ has a list of Bluetooth dongles that are known to work the H9 on Windows PCs: