This is a very buggy software made worse by the fact that causes are difficult to pin down. Sometimes it works, sometimes it doesn't without any logical or traceable explanation. It not only affects the basic burning software but also Spin Doctor. Without apparent cause, Spin Doctor refuses to record web content and offers a "help" that is not existent. I suggest that something is deeply wrong with Toast that requires a complete analysis by it creators. The software is awfully buggy and is not worth the money paid for it. I have been a Toast user for years now and the problems persist.
Interesting... I found out that my external LaCie burner will work well with Verbatim DVD-R discs. Not so with Imation DVD-R discs. With the latter I get the error but not with the former.