help with burning problems

Hi there,
I have a 24" iMac... that is 9 months old... I have burned lots of dvd's using toast, disk utility, finder... all good... however in the last couple of months my burn quality has gone in the crapper.... divx files burnt are choppy and unwatchable but the whole movie is there...and when you make it dvd video in toast the quality is also not very good(better than in divx but still not dvd quality)... any ideas as to what is wrong? I have run a hardware test and everything passes.... is there a separate test for the dvd burner?? very frustrated cuz I love my iMac but if the burner doesn't work properly.. it's no good! I am using philips DVD-R which I have gone through 100 of them and no problems til the last couple of months. Any help would be appreciated.

Have you tried cleaning the drive?

http://www.geeks.com/details.asp?invtid=F8E648-DT&cat=MED

Only a suggestion, you can find cleaning kits at most any store which sells computer accessories and media.

If cleaning does not resolve the problem, the drive may be defective. A nine month old machine is still under warranty.

Regards.