This article is from the CD-Recordable FAQ, by Andy McFadden (firstname.lastname@example.org) with numerous contributions by others.
http://www.adaptec.com/support/configuration/cdrec.html has some advice on
SCSI configuration. Basically, check your cabling and termination (see
section (4-17) for more advice there), turn off features you don't need,
and make sure Auto Insert Notification is off (see section (4-1-1)).