Old thread (sorry), but I've run into this, and decided to try using SysInternals ProcMon to see what was going on, as the program appears in Task Manager but its GUI doesn't appear for 5-10 minutes, even though it's using no CPU/not accessing disk or memory prior to opening the window.
This is really just intended as background info for Arturia, as there is a new post about MIDI Control Center not opening on Windows 10, and I would bet it's the same problem.
The comments here about external USB drives are interesting, as ProcMon shows it is repeatedly accessing a bunch of USB Registry entries, eg.
HKLM\System\CurrentControlSet\Enum\USB\VID_2833&PID_0211\WMTD304H4014J7\Device Parameters
HKLM\System\CurrentControlSet\Enum\USB\VID_2833&PID_0211\WMTD304H4014J7\Device Parameters
HKLM\System\CurrentControlSet\Enum\USB\VID_2833&PID_0211\WMTD304H4014J7\Device Parameters\DeviceInterfaceGUIDs
This device is described in the Registry as "@usb.inf,%usb\composite.devicedesc%;USB Composite Device", but MIDI Control Center cycles through a large number of USB devices and just repeats over and over until finally it gives up and opens the program after 5-10 minutes!
It seems the program must enter a loop where it tries to scan these entries in the Registry and gets stuck...