I thank you all for your answers.
As a matter of fact I did not have reading problems with my CD-RW, but I simply don't understand why a drive which can go 10x should not be able to go 4x!
It seems to me a kind of "software decision".
After all, when one buys such an expensive drive he should gain maximum flexibility or, at least, he should be able to do the same things he could do with a 4-year older model from the same brand!
I know that my desire to burn at low speeds can look absurd to others, but I could say the same things about others' desire to rip and copy commercial dvds or similar things.
The fact is that if you buy the (supposed to be) best product and consequently pay for it, you do that precisely because you expect it to be able to work without limitations whatsoever.
Anyway, anyone knowing if and how my "problem" can be solved?
P.S. As to the systems hungs, my 716A stands all alone, as master, in the secondary IDE channel. I cannot think of a better seat.