First, I want to thank you all for your responses.
Second thing, Darth Boy and rdgrimes are MORE than right ! My TEAC unit can ONLY re-write at 12X... I feel kinda stupid about this...well that's it: i didn't know what was the speed... I thought it was 24X....
I'm kinda newbie to this, but one more thing: I also thought that CD-R / CD-RW media are backward compatible so you can write at 10X for eg. Am I wrong ?
I'll go and buy some Verbatim now....and I'll watch for the speed