After re-installing Slack 9.1 (to get it back to a good working system again), I'm now able to burn using X-CD-Roast as well as command line both data and audio CDs. Thanks to everyone who helped.
BTW, after re-installing, I set it up so my cd-rom was ATAPI and only my LG burner was scsi emulated. I don't know if this was the root of the problem, but it works fine like that. So:
/dev/hdc still is ATAPI
/dev/hdd is now /dev/sr0
Hope this helps others out there.