WiFi with Exclamation mark after upgraded to Mountain Lion

Backup these 2 files:

/Library/Preferences/SystemConfiguration/NetworkInterfaces.plist

/Library/Preferences/SystemConfiguration/preferences.plist

Then delete these 2 files and reboot. If you upload these 2 files someplace I can take a look if something was wrong in there.

Is it still working?

Try ask Apple here: https://expresslane.apple.com/Issues.action

Hi Wfiguru, i have the same problem but do not have these 2 files... Would you pls have another thing for me to do?

Many thanks, efi

After trying all kinds of suggested solutions, I tried yours and it fixed the problem immediately. It was really annoying to have full internet access but see that stupid exclamation mark on the wifi icon.

Thanks.

This seems to have worked for me in solving the wireless connection-dropping issue since upgrading to ML. I've also noticed the internet connection being snappier than before.

Maybe this should be a normal housecleaning operation, just like running Onyx.

Most definintely. Ever since deleting those files and allowing OSX to re-create them I've not had any dropouts - that were caused by the internal Airport card.

I don't see too many "stickies" but somehow I think every 10.8.3 user should somehow be able to find this information easily - and quickly. I'll post it on my blog, but it would be nice if these forums had a way to make this a "must read" option for the masses.

Awesome. This worked for me. Thank you!!

Don't even have those files...

Like many others, I don't have those files in my prefs folder. Can anyone explain this?