OK I just installed CD Speed 3.8 which has been released since your post and all is well!! How odd that the version of CD Speed supplied in the retail pack didn't work with the drive!?
As an experiment, I burned a Princo 4X disc (I know they're crappy - it was just for a test) and then used CD Speed - I got a quality score of 73!! Is that a high score for Princo, it seems like it should be?
I live in NZ and am limited as to what brands I can get my hands on but in general would you agree that Imation DVD+R 8X should be reliable?