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A RW disc need to be "formatted" only if it must be used like a large floppy disc with the so-called packet-writing softwares.
If you don't use a packet-writing software to burn data on a RW disc, it is not necessary any "formatting".
For some unclear reasons, it seems that nero is not able to manage correctly RW media. Many people experienced better results with rewritable discs using ImgBurn. Try to do a FULL erase with ImgBurn and see if the disc can be recovered.
Keep in mind, however, that RW media natively contains more errors than write-once discs, and the amount of these errors rises with time: the more times you re-write the disc, the more are errors. Some standalones are rather picky about discs, and if a disc contains too many errors, they are not able to read the disc anymore.