740a

My problems began with decrypter not recognizing my dvd burner sometimes,this could be corrected with a reboot of my pc.Now my burner (Plextor 740a)is acting strange,It will not burn,read or write.When I insert a dvd the green light blinks about 5 times and goes out,Nothing happens!
I have burnt about 10 backups in the last week with no problems.This exact same thing happened a while back with a Nec 3540 burner that I returned and bought the Plextor.I have checked device manager and all looks well.I have a new Dell and both burners have been new.I am using dvd decrypter,shrink and nero 6.6.I thought the Nec was bad,but now the Plextor is doing the same thing.I have the Plextor installed alone in the master position.I also have ran anti-virus and spyware checks(no problems).Any ideas??