I just had a problem with the disc-at-once feature. Again. It got about 2/3 through the burn and stopped with no error message, nothing.
I had this issue (also with the Que 12x10x32x firewire drive) when the drives first came out, and it *did* get fixed in Toast Deluxe 4.1.1.
I was able to succesfully burn a CD the other night in the same configuration, but I'm pretty sure it was before I installed 9.1.