So the culprit was AirPortBrcmFixup then; good to know the issue is fixed with a newer version. I saw it also fixed a similar issue with a BCM4352 card in another Hack of yours. I never used that Lilu PlugIn with my DW1820A cards; never needed it and, as stated in my BCM4350 guide, when I tested the card with that kext, I always experienced slightly degraded performance.