Well, I've been experimenting. I've been getting perfect burns with the Memorex 2.4x DVD+RW and the Memorex 4x DVD+R blanks, but having lots of trouble with Verbatim 2.4x DVD+R blanks.
So, the folks on the various forums are right. The media does seem to matter at this stage. With the Verbatim, I get hangs and write fails, but the Memorex works perfectly with my older Sony DRU-120A (with Ricoh MP-5125 firmware). Caveat emptor.