This burner is old enough it may not recognize many of the newer disks available for burning. Every dvd drive has firmware in it that allows it to choose a specific burning strategy for each type of blank media you put into it, according to the mid code on the disks (manufacturer id code).
Mid codes that have come out since this burner was produced are not recognized, and the burner will either not function, or may choose a generic burning strategy that might not work well. You can go to the manufacturer's website and try to flash to a newer firmware, but it may not help much, depending on when the last firmware was released. It is the first thing to try anyway.
You could use media that has been around a long while and probably get a better rate of success. Verbatim 8x is still available, and even the 16x Verbatim might work with this drive. Taiyo Yuden 8x+R would be another good choice, though you can only buy it online in the US anymore (rima.com or supermediastore.com are two places that have it).