I have the exact same problem.
I was burning a lot of DVDs last night. I use Ritek 4x DVD-R to burn and I burn them at 4x (even though I have the 1.21 hacked firmware which enables me to burn at 8x). While I was burning one, I accidently left the speed at "maximum" and it burned the disc at 8x until 33% when the disc coastered.
I figured that the disc was stuffed, no big deal but now whenever I put a DVD into that drive it just makes a repeated clicking sound like the drive is trying to read the disc but can't.
I have tried taking out the drive, reflashing the firmware but it still doesn't work.