The problem is I have been through this so many times; DMA is enabled, I have the latest firmware, but downgraded back to 1.06 because 1.07 and 1.08 produced such bad burns, but even with 1.06 the drive has lost it totally - I'm getting errors into the 500-range from the same Verbatim stock I was previously getting sub-20s from with a previous RMA (But that had the evil Tray vibe problem), and with CDR's failing to be burned and even having underruns (Using TDK, Ridisk and some crap no-name stuff that I got from Maplins).
My 4x Mitsumi produced better quality burns (And in fact, produced working burns!) than this thing currently does, so I can only assume the drive is faulty.
I must admit that I am getting rather weary of all of this. I'm definitely considering like, an LG or another LiteOn or maybe even a BenQ right now and just cutting my losses with the 716, but I would have to waste lots of time doing even more research into finding which ones is best. Then again the reviews and stuff I was researching were what lead me to get a 716, so even those I'll have to be careful with...!
I suspect it is really a build quality issue; Someone mentioned they were appalled with the construction quality of the 716, and the fact that it seems to keep deteriorating on me does not bode well - this current drive was okay when I got it as an RMA replacement; Error rates and readability of CDR/RWs was rather mediocre, but within limits.
Now the DVD quality has dropped markedly and the CDR/RW support is practically non-existant!
sigh Anyway, wish me luck on the RMA...! 
