DMA Setings keep changing to PIO

[Keep_It_running]

I have an issue with the DMA settings changing to PIO. If I uninstall and reboot the Primary and Secondary IDEs show up as Ultra DMA5. But after a while the Primary changes to PIO. I have 2 600 SATA HDs and Two optical drives, Win XP sp2. This is killing my speed, of course and driving me nuts because I haven't run into this issue and don't understand all the influencing aspects that can control the DMA status. I only understand that if the DMA has trouble working it will try around 5 or 6 times and then revert to the PIO setting.