Plextor 755-SA issues!

I’ve had my Plextor 755SA for over a month. Now the drive starts burning at 8x on 8x discs, but after about 30% it slows down to 2x. It look like its trying to go faster but the buffer keeps running out!. Any ideas?

I’m using DVD Decrypter to burn.

did you find the solution?
I got the same problem and the drive is new.
I tried burning Verbatim 8x with Nero 7 and PlexTools Professional.