dd

This is driving me nuts! I can't seem to get dd to write an ISO file from a CDROM disk. Here's the command:

sudo dd if=/dev/cdrom of=cd_image.iso

Output:

dd: reading `/dev/cdrom': Input/output error
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.00442516 s, 0.0 kB/s