10.6.4 totally lunched my wifi, no doubt about it. Verizon DSl, Westell router, two Airport Extremes, I tried every suggestion for a fix and nothing worked. Zero, zero, zero. If the update screwed your network don't waste time with any system fixes or anything not related to network settings. You must create a manual DNS server. I joined OpenDNS to use their DNS server setting and for the first time in a week I have my home network back. The reason it was great for me is that you take their links and they not only step you through it, but tell you if it was successful. The second I followed the info for changing the DNS on my Westell router to Open DNS and told everything to just follow that I was back online after following every d@mn other advice Google found for a horrible week !!!! : )