I'm still guessing it's the card. I have had zero problems with my Sandisk Ultra II 4 gig card, which is rated at 60X. all of my recordings have been via S/PDIF from the V3, and the last couple at 24/48. In fact, tonight, I'm taking it out without my D8. (but, Scott and I are running a comparison of the V3 A/D at 24 bit and the ad2k+ at 24 bit, so in the event that my recording messes up, we'll still have his V3 > ad2k > laptop recording.) Anyway, I would suggest buying a faster card.
the lack of any problems on my end lead me to this conclusion. that's the only thing different from our setups, right? at least, that's the only thing I can think of.