Some users have reported loss of internet connectivity after the update to Mac OS X 10.6.4. These users have active IP addresses but cannot access any outside network services.
Fixes
Set manual IP address. It appears that some instances of this issue are caused by DHCP problems and can be resolved by manually setting the Mac’s IP address; follow these intructions.
Boot in Safe mode and apply combo update. Booting into Safe Mode may temporarily restore your Internet connection, at which time you can reapply the Mac OS X 10.6.4 combo updater, which may resolve the problem. To boot in Safe Mode, hold the Shift key while your Mac is starting up. After booting in Safe Mode, download the Mac OS X 10.6.4 combo updater, which weighs in at a hefty 887MB. Quit all open applications and run the installer.
Mike says
I have a MacBook Pro 2.5Ghz, unibody (Early 2009). After installing the 10.6.4 yesterday, I lost the ability to use my Ethernet Port altogether … Resetted PVRAM and SMC, cleared permissions, and downgraded to 10.6 SL … Not fixed … will have to take to Apple now, given that its out of warranty by 2 months .. I’m going to have to spend a small fortune for a new logic board and time wasted … really hating this state of affairs … It can’t be a coincidence that my logic board fried the very same day I did a 10.6.4 upgrade … too many people complained about this too in different ways. But Apple will say that its could never be a software issue, always a hardware problem … hating this week …