I have had three optical drives go bad on my on three different Macs. I had an auth. Apple reseller replace the one on my iMac, which complained of a servo error (hardware failure). I replaced the optical drive on my Power Mac G5 myself, and I just replaced the DVD burner on my 2 GHz MacBook Pro.
Symptoms on the last one were: spitting out good discs just after I put them in and failed verification in Toast. But replacing the optical drive on the MacBook Pro is not for the faint of heart. My MBP survived intact aside from my trackpad button, which is not as responsive. *
Good luck and let us know what you find out.
* BTW, if anyone has an idea about fixing the trackpad button on my MacBook Pro (2006 2.0 GHz Core Duo), please do tell. It used to work flawlessly, clicking reliably no matter where I pressed it. Not since I took the machine apart. I don't know what I did.
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