Q: iMAC 21" WIFI failing after 10.7.4 update

This is a fascinating thread, because I've had this wifi dropout problem since Lion 10.7.0 (documented elsewhere).

I went back to Snow Leopard a long time ago but keep an installation of Lion on a separate drive for testing.

I was trialling 10.7.4 last night to see if this bug has finally disappeared for my 2010 iMac (Lion is unusable to me because of this - Snow Leopard works flawlessly). I've tried 10.7.1/2/3 with no success, but now I see you guys, on 2011 models who never had this problem on Lion before, have now got it on 10.7.4 - it's like a disease!

I just wanted to mention this background to you newcomers... welcome to this bug. Get comfortable.

Same issue here...Mid 2011 iMac, 27", 3.4Ghz i7, 16Gb RAM - after 10.7.4 drops WiFi and needs a complete reboot to get it going again.  Then, sometimes it drops again and sometimes it does not.  Windows PC's, MacBook, 2 iPads and 2 iPhones all work fine on the same network...

Let's keep our fingers crossed for 10.7.5 and a fix!!

Same problem here. Lion 10.7.4, 27" imac 2011, Airport Extreme.

I have been writing whenever I can to encourage people to try the following solution that was posted elsewhere in the Apple discussions.

Go to: Library/Preferences and delete the SystemConfiguration folder. Reboot. The system will remake this folder. Evidently, some file in this folder gets hosed and needs to be remade.

I saw this fix in someone's post on May 25, 2012. I tried it and it worked immediately for three Macs I have. It has been working great for three days now. On May 27, I installed 10.7.4. The fix is still working. I had been experiencing severe wifi network drops requiring the usual procedure of turn off wifi, turn it on, then connect to the router. Now I dont' do anything. It works after reboots, after logouts and then logins, swithes to other users and back, etc.

There is nothing to lose by trying this. Hopefully it will work for some of you experiencing this problem.

Please let us all know your experience with this fix.

Apple Care gave me this solution by phone and it didn't work.  I was already running 10.7.4 at that time.

Were you running 10.7.3 when your wifi drops began?

As Phildkc experience, Apple Care gave me this solution by phone and it didn't work.

It sounds like you are having a slightly different issue. Turning wifi off and back on does not work for us. We are having to reboot the whole mac - are you using mid 2011 iMac, my other Mac is fine.

FYI I have rolled back to 10.7.3 and no drops for several days now. Not ideal I know!

Guy

See my post on the previous page. With one small exception, my Sharing has been working non-stop for 24 hours. When it stopped working I shut down and restated my iPad and it was working again. It is completely weird and random I think, but it seems, at least for me, that turning off the security on Sharing on my iMac seems to be the most reliable method for now.

I did a couple of other things, look at the post on the previous page, but aside for turning off the security, I'm not sure what else is making a difference. This has worked for others.

Apple: Please release a fix for this! Thanks.

Today I used Software Update for 10.7.4.  After re-booting, Safari hung up after connecting to a website.  I noticed WiFi was not connected and the iMac was frozen. I had to use the Power button to shut down. After re-booting, I was able to get WiFi thru Network Properties. I immediately download and installed MacOSXUpdCombo 10.7.4. I am not sure if it was a re-install or added files from earlier update, but that doesn't matter.  It has been working for several hours since then. So far so good. Maybe this will work for others.

I have a 2009 Late imac. Can't figure out how old the Mac Book Pro is, but probably 2008. Also a Macbook from about 2007. The first time I had problems was with Lion. Although after upgrading to Lion I also upgraded to an Actiontex N router from an earlier Dlink G router from Verizon.

I could not determine whether the problem was router related or Lion. But now I am sure it was Lion. The last time I had a problem was under Lion 10.7.3. I implemented the fix I mentioned under 10.7.3 and it fixed the problems on all three computers. I then upgraded to 10.7.4 and have not had problems with it either.

I did have a short interlude of a few minutes where I lost lock with the router and had to reset the wifi. That was on May 27 and only once. I attribute it to a router problem or minor instance probably not related to the fix.

Sorry, if this does not work for folks on this thread.

Thanks - I'm the person in this thread with a problem on a MacBook Pro that couldn't remember its preferred network after I moved to 10.7.4, and the fix you suggested of deleting the SystemCOnfiguration preference file seems to have taken care of this issue.  The new preference files are a lot shorter than the previous ones, and it is no longer having a problem getting to the preferred network.  I no longer have to choose a network manually each time I awaken the machine from sleep.

Agree with the randomness of the wifi drops.  No descernible pattern that I can detect.  For me a temporary solution has been to change from WPA authentication to WPA+WPA2.  A forum post here suggested moving to WPA2.  I've had only 4 drops since 5/24, none in the past 2 days.  However, upon boot up the iMac is unable to connect to wifi and presents a window with SSID's it can see including mine.  Once I click on the correct SSID the iMac logs on and things are relatively stable.  Seems a bit odd that changing security affects the drops and that I have to choose the correct SSID.  Just an observation, not a complaint.

Yes, my drops are random as well, and the 'not connecting to wifi' after sleep has also started happening again.  I have a brand new (purchased in Feb 2012) 27" imac.  It was running 10.7.3 when I purchased it and it has had a constant wifi dropping problem since about week 2 after purchase.  I called applecare and was given the update for the 'not connecting after sleep' issue. Plus a bunch of other workarounds/fixes that have not worked. I don't believe that it is a hardware issue as I've taken the computer into the apple shop and I have had the wireless card replaced.  Still experienced wifi drops.  Then 10.7.4 came out, and I quickly upgraded as I have been hanging around on these threads for the past few months hoping for some magical fix (I've tried everything, including a reinstallation, and replacing the wireless card)  Not only did 10.7.4 NOT fix the wifi problem, but the wifi issue has gotten worse - It doesn't automatically connect when you reboot the computer (I have to select it manually) the 'not connecting after sleep' issue has reappeared (and the fix that I was provided a few months ago from apple is not compatible with 10.7.4)  This is really disgusting...a wifi compatible computer that can't connect to the internet wirelessly! You guys know that there is a problem - FIX IT!

This solved my wifi dropping problems:

http://www.appletips.nl/os-x-10-7-4-fix-voor-draadloos-netwerk-problemen-imac/

Use Translator to translate.

I did this just now and solved my problem too...yyeeesssss!!!! It's a very simple procedure, fantastic!

My iMac 22.5" mid 2011 dropped wi-fi after updated to 10.7.4 since a month ago, but now it's working fine again, solved problem completly.

Thanks a lot and congratulations!!!