Unable to enable DMA on my DVD drive

[Adam Membrey]

Hi, I'm trying to enable DMA on my Pioneer Drive (DVD-RW DVR-108) as I'm 
experiencing gradual but huge losses between audio and video whilst 
watching DVDs using mplayer. I'm using sudo hdparm -d1 /dev/hda and I'm 
receiving the following error message:

/dev/hda:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Operation not permitted
 using_dma    =  0 (off)

I do have throttling using powernowd but would that be affecting the 
loss I'm getting in any way?