iMac 2011 - no wifi connection after sleep under Lion

Right I tried Wills suggestion but it didn't work and I re set my router and that failed too. So I have done everything the the guy in the genius bar suggested and what's on here. I am 99% convinced that it is a Lion software problem and I wish Apple would sort it out. I am sorely tempted to go back to a pc at this rate 😟.

Each time the forums go quiet, and I think Apple may have solved this issue, and it might be safe to try and install Lion again, someone posts about it still being an issue, and I get frustrated ...

Ashley, I left a message with the guy at apple dealing with this issue / my case, so hopefully he will get back to me soon with an update. I will post on here when he does. I thought everything Apple was seamless!! - apparently not.

wanted to say I was having same issue with imac 27" summer 2011. Deleted the files and its working for me...!!!! thank you!

I was having this issue as well .. I tried making a new location, deleting keychain passwords, finally deleted the plist file (after saving a copy) and it would auto connect with no problem. This would happen periodically under Lion but mostly after replacing my Linksys router with an Airport Extreme.

I realized when it rejoined after deleting the plist file that the password type had changed from WEP to WPA2 Personal - so I went back into the old plist file, modified that string, and put it back into the Library/Preferences/SystemConfiguration folder. No further problems.

I finally tried the suggestion posted by Ocalawill on 12/5/11 without success. In response to brengamgee's 12/16/11 post, my security settings were correct when my Wi-Fi was re-established. Nothing seems to help this issue, and it means I am unable to sync with my MBP unless I walk the 150' to where the iMac is located, re-connect to WiFi, return to the MBP, and perform the sync operation.

Worse still is that the iMac is unable to back up to Time Machine/Time Capsule. Big problem. Hope Apple pays some attention to these discussions.

I recently spoke to an Apple rep in Orlando when there on business. The general view was to do a back up and take my iMac to an Apple store and do a complete clean install of Lion, which might help. The rep said they are not told anything by Apple until it happens, so they don't know when the upgrade to Lion is due.

Brengamgee, if I have read your post correctly, the only problem is WPA2 is a much better encryption system, but it should still work.

So Apple please can you fix this as I am very disappointed with the support so far.

I have a multi-platform network running here - two PCs (one with Vista, the other with XP) both of which sleep and wake, connecting to the network automatically just fine.

I have an iPad, as well as two iPhones in the household. All of which connect to the wifi automatically just fine too.

I have an iMac, which I purchased mid-2010, running snow leopard. It connected to the wifi just fine. For a while, I had it with no auto-sleep active, because I needed to access it remotely, but I have since removed that feature. It was also hardwired to the network so I have no idea if it had the sleep/wake wifi issue.

Late September of this year, I purchased a MacBook Pro with Lion. It sleeps/wakes and autoconnects to the wifi just fine.

My iMac, however, does not. Since I decided to take it to wifi only - at the beginning of December - that's when I discovered the problem.

It is frustrating in that I need to rightclick the wifi icon, select my home network, and tell it to connect. It doesn't take very long, but it's frustrating when I forget then open up Safari and find out I have no network connection.

What's weird is that my MacBook connects automatically just fine, while my iMac does not. My working theory, based on what I've observed, and what I've read in some messages here, is there's an issue when people upgrade to Lion from Snow Leopard.

That said, the benefits of the upgrade to Lion outweigh the inconvenience, imo.

--SOLVED (I think)--

(for me, anyway)

WHAT I DID:

Opened up networking preferences.

Opened up WIFI preferences.

Deleted all settings.

Went back to device configurations

Deleted ALL configurations - WIFI, Firewire, Ethernet.

Created new WIFI configuration

Checked "Ask to join new networks" checkbox <---- This, I think, is the key.

Then... to test:

Put computer to sleep

Woke computer up

WIFI connected automatically.

We will see if this still works after my computer has been asleep for a few hours.

I think the "Ask to join new networks" checkbox is the reason I was not automatically connecting. It's a simple thing, but when you read the text that goes with it, it says, "Known networks will be joined automatically. If no known networks are available, you will be asked before joining a new network."

I don't think the text found at the checkbox is worded as well as it could be. Perhaps radial switches instead:

Join known networks automatically; otherwise ask first

I will connect to my wifi network manually every time

Just a thought for whoever at Apple is reading...

Today, I ran into the same issue. When I woke up this morning, my 24" iMac was not online and there was a message, that said "There is another device using your computers' IP address, try reconnecting" or something like that. I tried everything under the sun, but in the end, what solved my issue was me unplugging my router, my wireless router, unplugging my Apple TVs and turning off my wifi on my iphone. Then I plugged my provider router in, waited until it started to broadcast again, then I plugged in my wireless router and waited for it to do the same.

Once that was done, I then powered on my iMac first (so that it receivedd a good IP address) my ATVs (one at a time) and making sure they connected before powering on another. By the way my iMac connected without a hitch, because it was the first device to connect.

I hope this helps. It worked like a charm for me.

Good luck everyone.

--UNSOLVED--

When my iMac goes to sleep automatically, it does not reconnect upon waking up. However, when I put it to sleep manually, it does.

If I wake it up after going to sleep automatically, put it to sleep manually, then wake it up, it connects.

Alrighty then!

I actually unchecked "Ask to join new networks" as I think this was the cause of my iMac not knowing which network to choose after going to sleep. With an iMac, I don't want to join any other networks so why have it checked? The Apple's store network was listed from the time we set up my iMac in the store. I deleted that and only kept my network as a possible one listed.

If one goes into your advance section under network, is the "Remember networks this computer has joined" checked? I think that is more imporant than the "Ask to join new networks" box.

I just went and looked - yes, that is checked, so that's not the cause of the problem.

As I mentioned, my MacBook connects fine, so there's something else going on.

Seems like you are just having a bad time there.

All I can really suggest and this is the best way to get the answers you are looking for, since none of our ideas have worked, is to make a Genius Bar appointment, at you local Apple store and be seen by the Apple Crew. It's free to look at. I've done it a few times. They are great group of people and their job is to find the answers, so....yeah, that's all I can really say now.

I hope you find a solution to your problem.

Try this:

System Preferences > Network > WiFi > Advanced > TCP/IP tab: Configure IPv6 "Link-local only".

After trying numerous other fixes, this appears to have solved the problem for me. Since changing IPv6 to "Link-local only" Lion has never failed to reconnect after waking from sleep.