Very strange...I'm having a similar problem with this drive (my second one, the first did the same exact thing after a time)
Trying to burn a DVD+R w/ ImgBurn, and device buffer keeps dropping to 0 & up again, then back, so burn speed won't go above 2.5X.
SATA cables were brand new both times, drives worked great for about 6-8 months, then basically become useless. My 2nd SATA drive , an Optiarc , is older than both of them were & still works flawlessly. Don't think I will spend $$ on Samsung again.