image from CD

[gusti <ggh.develop@gmail.com>]

Hello,

In the past I remember using the command "dd" in order to make an 
axactly image copy of some cd. But now the command "dd" does not work 
anymore.
The dmesg give:
   usb-storage: waiting for device to settle before scanning
     Vendor: Slimtype  Model: DVDRW SOSW-852S   Rev: PSX3
     Type:   CD-ROM                             ANSI SCSI revision: 00
   sr0: scsi3-mmc drive: 24x/24x writer cd/rw xa/form2 cdda tray
   sr 48:0:0:0: Attached scsi CD-ROM sr0
   sr 48:0:0:0: Attached scsi generic sg0 type 5

but if I try "dd if=/dev/sg0 of=cd.iso" nothing happen, in the other way 
if I try "dd if=/dev/sr0 of=cd.iso", then I get:
   pr100:/mnt/data4/root# dd if=/dev/sr0 of=cd.iso
   dd: reading `/dev/sr0': Input/output error
   0+0 records in
   0+0 records out
   0 bytes (0 B) copied, 0.00694673 seconds, 0.0 kB/s


So how can I make and exactly image CD copy?

Thank you in advance, Gustavo