UDMA Problems wit Abit NF-S Rev. 2.0

[M.D]

Hi
i have a nforce2 motherboard and a lot of trouble to activate the udma 
mode for my dvd drive, already tried all hdparm combinations with this 
result:
/dev/hda:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Permission denied
 setting xfermode to 66 (UltraDMA mode2)
 HDIO_DRIVE_CMD(setxfermode) failed: Permission denied
 using_dma    =  0 (off)
anybody with the same problem and an idea how to solve this ?