Plextor Tech Support replied
"It could be caused by uninstalling the PlexTools Professional(PTP) as remaining speed setting of "Silent Mode" at 4x.
This case, the speed setting is still effective even though the PTP has been uninstalled.
As for solution, pls re-install the PTP, press "Reset Values" button of or disable Silent Mode and confirm the write speed option again."
well i did as told .i check and uncheck every Rec there is in the drive settings. namely VariRec/GigaRec/Silent Mode/Securec.
Read speed is up to 40x and cdr is back to 52x~.
Nero also detect the correct speed .
after i shut down and restart the pc ..same things happens again.
stuck @ 4x write.
Updated to Firmware 1.02 .same thing~.after restart down to 4x again..