Using Nero CD Speed (http://www.cdspeed2000.com or if you already have Nero installed on your system, CD speed will be installed already as part of it), place a DVD disc which you have already written to (non-blank) and run a burst rate test. Post the results here.
How is your H10A connected to your system? As in which IDE cable, primary or secondary; is there any other device sharing the cable with your H10A? And if so, what is that device?