Like some others in this forum I had problems burning CD-R with my plextor 712sa. It would read and write all kinds of DVDs, but only READ CDs. I could not write in Nero or perform a write test with Plextools. The drive would freeze and the only way I could open the drawer was by doing a HARD reset.
Solution for me was to use the newest original NVidia nForce drivers (6.53) from the Nvidia download page. I guess it has been incompatibility with the older Nvidia IDE drivers. The newer ones work extremely well (at least for me).
DFI Lanparty nF4 SLI-DR
712SA connected via Port2 of the NVidia SATA ports.
Hope this helps...