why does my oregon 300 does not start up when the usb cable is plugged in i?

When I switch on my new oregon 300 after I have plugged in the usb cable. de gps hangs. i have to open the instrument and remove one battery and start over without cable plugged. if the oregon 300 is already on, i can connect to the pc, but when i want to switch from mass storage mode to rec mode i hav to unplug and re plug again. no good for the connetion i think.......