Airport wont pick up any networks after sleep

I'm having the exact same problem with my new 27" iMac. I find that if I turn the airport off before putting it to sleep and then turn it back on once I wake it, it picks my router up most of the time, but not always.

I understand that the upcoming OS 10.6.2 release is to address, among other things, Airport on the late 2009 iMacs. Whether it will fix this particular wake from sleep issue, however, remains to be seen.

My 21.5 is doing the same but also happens if I have just not used it for a few hours but left it on, especially in the evenings, like you it finds hub ok all the rest of the time, the first time this happened I ended up moving my hub thinking that was the problem, glad it isn't just me!

There has been a problem on certain Mac's for years with trouble re-connecting to wireless networks, this is a slightly different problem, but the same workaround might solve it.

1. Move "System Preferences.app" to "Applications\"
2. Delete all preferred networks in Network Preferences
3. Delete all Airport password in Keychain Access
4. Restart
5. Choose network from drop-down menu and enter password
6. Restart

My dad is experiencing the same problems with his brand new iMac 21,5". WiFi works flawlessly until it goes into sleep. Reconnecting requires a restart.

Can anyone confirm if this issue will be addressed in 10.6.2?

To answer my own question:

"AirPort

Resolves a performance issue on new iMacs."

From the 10C540 changelog.

Pullapartboy
I have been trying what you say and it works, I either turn off airport if I know i am not going to be using it for a while or turn airport off and on again when I return to the machine it makes a temporary fix whilst we wait for 10.6.2

I have the exact same issue with my new 21.5 Imac. When it goes to sleep for a long time it does not pick up ANY wireless networks after it awakes.
This is starting to a big problem because the only way to solve it is to boot the computer and I usually don't do that for weeks in order to be able to leave open a lot of files and programs.
So, when is this going to be solved?????

My new iMac (two weeks old) is having some of the same problems. Additionally it will at random just lose connection with my time capsule (and my other router). I cannot see why it is doing this but it is. My mid 2008 macbook pro has no problems staying connected though so I am hesitant to say that it is all software related.

Anyone else having similar issues?

Hi everyone
last night lost the wireless connection and did what I thought worked ie turning airport on and off and it didn't!
As I have apple support I will try and ring them today to see if there is anything they suggest, not sure if anyone else has tried but will feedback.
have a good day

right I spoke to Apple and this is what we did
click top right screen on magnifying glass
type disk and enter
shows disk utility
click on it
click on macintosh hd
and then click on repair disk permissions it took about 3 mins
whilst doing this it did come up with a file that it couldn't repair - which he said was ok to ignore

once this was finished we put it into sleep mode and it connected to the wireless straight away.
I obviously need to test this some more and as I have lots of jobs to do today my computer will be resting most of the day so will see if this sorts it, if not I will contact apple support again

Here is what the apple rep told me to do:

Go to the Library folder on your HD
Then go to Preferences, then System Configuration
Inside the System Configuration folder delete these things:
com.apple.airport.preferences.plist (I had three of these, delete them all)
networkinterfaces.plist
preferences.plist
restart your system

After completing these steps my iMac has found my time capsule and stayed connected for a half hour. It has even completed a backup where backing up last night was disconnecting me. Hopefully this will keep it working long enough for them to put out the 10.6.2 update.

I am having the identical problem. I'm also in an apartment building where there's usually 15 other networks to be found. But when it wakes from sleep the AirPort icon has an exclamation point and it finds NO networks. I've tried everything to revive it but nothing works except restarting the iMac (which fixes it every time, but is obviously inconvenient).

Ok, so that fix worked for about two hours and now it is doing the same stuff all over again.