I have connected this device as root and I have run
all commands as root, but i get numerous errors from
this device.

[17180102.492000] usb 2-1.2: new full speed USB device using ehci_hcd and address 7
[17180102.584000] usb 2-1.2: configuration #1 chosen from 1 choice
[17180102.584000] pl2303 2-1.2:1.0: pl2303 converter detected
[17180102.588000] usb 2-1.2: pl2303 converter now attached to ttyUSB0
[17180256.624000] pl2303 ttyUSB0: pl2303_open - failed submitting interrupt urb, error -28

ls -l /dev/ttyUSB0
crw-rw-rw- 1 root dialout 188, 0 2006-11-13 07:02 /dev/ttyUSB0

minicom: cannot open /dev/ttyUSB0: Protocol error

T: Bus=02 Lev=02 Prnt=02 Port=01 Cnt=02 Dev#= 7 Spd=12 MxCh= 0
D: Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=067b ProdID=2303 Rev= 3.00
S: Manufacturer=Prolific Technology Inc.
S: Product=USB-Serial Controller
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
I: If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=00 Driver=pl2303
E: Ad=81(I) Atr=03(Int.) MxPS= 10 Ivl=1ms
E: Ad=02(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=83(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms

Thanks for any help or pointers.