No wifi connection on my imac G5 although wifi signal is 40%

Question

I have this very strange situation were I have a decent wifi signal ( measured with iStumbler 42%) on my mac, but impossible to get a connection of the mac with the wifi access point ( ping ; no route to host, or many packet loss, or very long ing; 2 to 2 sec)
I am using channel 12 nad istumbler says it is the only equipment inthis chanel

Answer 1

Hello,
Make a New Location, Using network locations in Mac OS X ...
http://support.apple.com/kb/HT2712
10.5, 10.6, 10.7 & 10.8…
System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.
10.5.x/10.6.x/10.7.x/10.8.x instructions...
System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.
The interface that connects to the Internet should be dragged to the top of the list.
If using Wifi/Airport...
Instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.
For 10.5/10.6/10.7/10.8, System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...
208.67.222.222
208.67.220.220
(There may be better or faster DNS numbers in your area, but these should be a good test).
Click OK.