I don't know if anybody has ever come across this problem, but I thought it might help others if I shared this.
I have a Sony DRU-720A burner and have used DVD Decrypter and DVD Shrink for several months with no problems at all. While trying to burn disk #6 of Buffy the Vampire Slayer Season 2 I received an "invalid handle" error message. In an effort to combat the problem I downloaded DVD43. To make a long story short, the problem was never really resolved, I just had to omit the menus and just put the episodes on the dvd. However, from this point on every time I tried to burn something I received a write error about 10% of the way through the burn process. I tried everything, including updating firmware, and nothing worked. Finally, I realized the one thing I had done differently since my last successful burn was installing DVD43. So I uninstall it, and sure enough, everything works fine again.
I'm not sure why DVD43 was causing problems, but like I said, I wanted to post this in case somebody else was having the same problems.