Burning speed problems

Hi, folks. I have a NEC ND-4550A DVD-RW and it began to behave strangely. When I want to burn a CD-RW with it, it would show in my recording program (both Nero and Alcohol) that the only speed available is 10x, no more no less. And it would show this speed regardless of which CD-RW type is in the drive, be it 4x speed or 10x. Of course when I try to burn a 4x RW with a 10x speed it pops an error. What could be wrong with the drive? What can be done about it? Thanks in advance.