exclamation mark in the wifi sign

Did you reset the airport yet? Try that first.

I get that every time the network monkeys start fiddling around with the configurations on the Cisco access points. Always want to blame my Mac, but it always clears up when they leave the access points alone.

Try turning Wi-Fi off and on again on the Mac to speed up the process.

I'm having this problem too! Anyone have an answer? Am on 10.8.2 on a late-2008 MacBook as well. Have tried tossing the plists and rebooting, that works initially, then exclamation mark returns. Renewing DHCP lease works for about 5 seconds before returning to the exclamation mark. After about 5 minutes or so, my connection will return, but it's about 5 minutes each time of the exclamation mark. Two other macs in my house, one on 10.7.3 and one on 10.8.2 also are NOT having this issue at all, or any connection issues for that matter. PC also not having this issue. Seems to be only my machine. Have restored router and rebooted it each time regardless, but the problem is with my machine, clearly, not the router. Help?

Try going to network utilities, and recreating the network there,

We have tried everything here... well, short of replacing all (four) of our wifi routers. This is an epidemic problem that is affecting most of our newer/fully upgraded Mac users (but not older equipment/older O/S). We've tried just about everything suggested in the forums, nothing provides a permanent fix (but sometimes we get a temporary fix, e.g. day or two, until the problem comes back).

We have four different wifi Apple routers (two Airport's and two Extreme's). They cover the entire office area. People with newer/fully upgraded Apple computers still experience intermittent wifi problems... but none of our Windows and non-Apple users have the problem. Our VOIP system and other devices stay online. It is only the poor folks with newer MacBook Pros or recent model/fully upgraded Macs that have the problem. At the same time we have some older Macs that do not exhibit the problem ever. Based on these observations we have come to conclude it is 100% a problem the either 1) recent O/S updates, 2) recent Apple hardware or possibly, 3) the combination of both of these.

The really frustrating thing is, once my own MacBook Pro Retina loses its wifi connection, it's very hard to get it back. Even after a reboot it often does not come back. Recently I've takent to doing a reboot along with PRAM reset, and that seems to solve the problem -- but OMG what a bloody pain. I can't believe Apple is still ignoring this issue after so many people have reported it, and so much time has gone by. I'm just hoping it can be fixed. My fear is that it's a permanent hardware issue that would require a new chip (or something like that)... and who knows if Apple would bother with a hardware recall. Bah.

PS...Our IT guy is now fed up with the issue. If we bring it up, he says, "Yea, there's two solutions: 1) keep rebooting until it works or 2) get a Windows PC."