Powerbook will recognize burned DVD-R but not blank DVD-R

I've been trying to Burn an .iso file onto a DVD-R disc but when I put the blank disc in, it just spits it out. Comp will recognize CDs, and burned DVDs of the same kind (Sony DVD-R 4.7 GB)

I've been looking at threads w similar problems but there hasn't been definitive answers. I have a MATSHITA CD-RW CW-8123 but don't know what that means. When I look in system profiler, there is no mention of an optical drive but obviously there is one. The only problem seems to be BLANK DVDs.

I'm out to get a "head cleaner" for my drive but is there any other diagnostics/remedies I can try before I shell out a couple hundred dollars at the apple specialist shop???