The answer is that Orinoco provided a settable option in their PMCIA to give robustness against microwave ovens. We believe that this option is the one that Apple calls "interference robustness". The key to this option is that microwave ovens have a strong periodic component to their radiated power. For 60Hz ovens, at least,, they spend 8.3ms radiating strongly, and 8.3ms being quiet, out of a 16.6ms period. Now, if a PMCIA sees interference, it'll slow down the transmission more and more. At some point, the packet size takes longer than 8.3ms to get out, and such long packets will get whacked every single time (at least by a 60Hz oven) - not just occasionally. What the option does, I think, is to prevent the PMCIA from ever backing off to packet sizes that are longer than this. Clever. Basically keep the PMCIA from shooting itself in the foot as it valiantly tries to keep up.