First question is what versions of Hoster and Microstudio are you using? For the Plextor PX-760 to work with those programs you should have Hoster 3.300 or higher and Microstudio 2.612 or 2.613.
If you have those versions then check this knowledge base article for other causes.
http://www.mtu.com/kb/index.php?acti...1ada6dec1479bc