DVD read/write errors

Vista
Asus P5B-VM
Intel Duel Core
Samsung SH-S203B Burner
Maxrix DVD-DL Media
Roxio easy Media Creator 9

Hi:

I am in the process of copying a number of DVD's. About 10% of my copies
contain errors that are not identified during the write. By read errors I
mean that when I play them on my DVD player they hang somewhere during the
playing. If I make a second copy the second copy works. I sometimes do
other work on my computer when my system is writing the DVD.

At about $1.00 a DVD-DL I am anxious to solve this problem.

Any thoughts as to why this is occurring?

FRED