When you use a single USB bulk storage device (for example, an iPhone) with a Windows-based computer, the device appears unresponsive. This issue may occur when following conditions are true: The computer has a chipset from the Intel 5 Series or the Intel 3400 Series families of Intel chipsets; The USB device has pending control and bulk traffic. This issue occurs because the Platform Controller Hub (PCH) cannot resolve which traffic type is a priority. Therefore, the port that is associated with the USB device stops responding. This issue occurs when the processor is in the C0 power state for a long time. For example, Cx states are not enabled, or system traffic prevents the system from leaving the C0 power state. If Cx states are enabled, the device may recover a short time later, explained Microsoft in KB978789. To resolve this issue, contact the computer manufacturer or the motherboard manufacturer for an update to your system BIOS.