ATAPI DVD A DH16A1L won't recognise blank dvd

Hi,
I re-installed my cd/dvd drive after the DMA turned off. The DMA is back on but now the drive will not recognise blank dvd's (+R or -R). The drive will play dvd movies but when i put in a blank dvd it recognises it as a blank cd on the cd drive. I have checked the cables in the drive and they are plugged in fine. I have also removed all my burning software and tried to delete the upper and lower filters but their are none there ( I followed the instructions from the HP Compaq website). Any ideas how to fix this??
Thanks