iMac WiFi connection to my router is unstable I got an iMac about half a year ago (2011 version). It has been fine, until recent weeks. Now the iMac loses its connection to my wireless router frequently. I have to turn off WiFi on the iMac and turn it on again to reconnect.

First I thought it might be the problem of my wireless router. However, in the same room, my Macbook Air and iPad work just fine.

I've done all the software update available. Still doesn't work.

What can I do to fix the problem? Any idea?
The problem resolved after installing the newest Wi-Fi update.
http://www.macrumors.com/2012/02/24/apple-releases-imac-wi-fi-update-v1-0/

EDIT: after upgrading to Mountain Lion, the same issue occurs again. Anybody encounters the same problem?

Tried to install http://support.apple.com/kb/DL1501. But the package prompt out that 'The package require OS X 10.7' which means not be able to install on 10.8.