Plextor 24/10/40A Writer..
Unable to write at 12x or higher up to 24x. Nero, Cdrwin, discjuggler all spit out the disc saying pma calibration error. But i I burn at 8x it will burn the disc, otherwise anything higher it won't even start burning.

How do you reset the power calibration?

you dont - you need different media

Cleaning the laser may help also, i've had this a few times with plextors and they were ok after cleaning (the type you get for a hi fi is ok to use)