did you try the "Reset DMA Tool" in TimC's signiture?
No optical drive can perform @ ultra DMA mode 5 so I think that is refering to your hard disk. Are no other devices listed in either the Primary or Secondary channels? Try uninstalling ALL channels listed and then restart.
You can also download cddvdspeed and test the transfer rate for both cds and dvds in your drive. http://cdspeed2000.com/files/NeroCDSpeed_4750.zip
You may not be able to run the transfer rate test with a retail DVD movie. So try and use a recorded dvd.
Both cds and dvds should read back with at least a relatively smooth curve.