dvd writer/burner not working no more in powermac

you could try resetting your pram or nvram ... or you coud get a new burner. I bought the pioneer 111D recently and it works fine (though it is still unsupported).

Or, if you installed any firmware recently that might have caused problems you might want to check with the manufacturer to see if it is a common problem and if they have a fix. I would not recommend wasting your money on lens cleaners etc. to troubleshoot your drive. If you have them, use them, of course. The cleaning kits cost almost as much as a new drive though!

Finally, you should also check apple support pages.