Your old CD-RW discs are probably rated for 2x maximum. CD-RW media have a different physical structure than CDR discs and have maximum speed limits pre-encoded on the disc.
The LG 8520b can write to CD-RW discs at a minimum speed of 4x. Therefore, your old discs are incompatible for rewriting with the LG drive, although they can still be read.
It isn't a software consideration, but a hardware limitation. Short of using an older CD-RW device which can rewrite at 2x, there is no way to reuse these discs.