DVD+RW OK but Not CD-RW?

Have upgraded to latest Nero InCD and can still ONLY use DVD+RWs. I have no luck with burning CD-RWs but have continued and reliable success with DVD+ and - RWs; any brand, several speed, and on two different DVD burners. Can anyone explain why I can burn DVDRWs but not CDRWs ? Thanks.

What speed and make CDRW’s?

I can no longer use 2x speed CDRW discs in my new DVD burners as they are unsuported.

-edit- and what burners are you trying them on?

Have tried Memorex 24x and 4x, Fuji 4x. They used to work but now do not. Some were even brand new; right out of the box. I have a Pioneer DVR-108 and Sony DVD Writer 200j. Any speed and brand of DVD rewritables seem to work consistantly.