Serial can't find my devices

[mgrouch]

now

unplug your USB-GPS temporarily from USB, REBOOT and do

lsusb

as pi user

First lsusb with the usb-gps unplugged (the pi rebooted after unplugging it). Second lsusb with the usb-gps connected - AND NOW IT SHOWS IN SERIAL!?!    

Code:

pi@openplotter:~ $ lsusb
Bus 002 Device 002: ID 0781:5583 SanDisk Corp. Ultra Fit
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 046d:c52b Logitech, Inc. Unifying Receiver
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
pi@openplotter:~ $ lsusb
Bus 002 Device 002: ID 0781:5583 SanDisk Corp. Ultra Fit
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 046d:c52b Logitech, Inc. Unifying Receiver
Bus 001 Device 004: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port / Mobile Action MA-8910P
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Now keep it plugged into USB and reboot. 
What are the results after that?