USB MIDI interface

Hello, everyone. I have a ESI M4U XL, the USB MIDI interface. I tested this M4U with my PC(64Studio 2.1 installed). I just plugged in M4U to USB slot of PC, and snd-usb-audio module detected M4U very well, and It worked fine. But, there is a problem. snd-usb-audio module detects M4U only when I plug in it to an USB slot. If I reboot my PC while M4U is connected to an USB slot, snd-usb-audio can't detect M4U. Anybody to help me?