CD-DVD Speed blocks Plextor drives due to the way genuine Plextor drives (those that existed before...2007?) were set up to scan with Plextor tools only.
For these newer drives that are merely rebadges of other hardware, you might be able to tweak a setting via the Windows registry to enable it. See http://club.myce.com/f105/samsung-sh-s182f-cant-use-disc-quality-under-nero-cd-dvd-speed-219336/ and make sure you remove the reference to "Plextor" where appropriate. This might work for that drive because...
This "Plextor" is a LiteOn.
That LiteOn is based on unreleased Optiarc hardware, but assembled & programmed by LiteOn, from what we gather.
Optiarc hardware traditionally supports some forms of limited scanning. LiteOn drives very much support scanning.
What other utilities have you tried?