WiFi trouble since Snow Leopard Upgrade

My WIFI does not work on someones time machine router. Older macs in the network connect. If i reboot the same computer off a 10.5.x drive than it works fine.

100% a snow leopard bug!

Ok maybe this will help: You get free support from Apple for 90 days on your software purchase. http://www.apple.com/support/

Bottom left of page you can call them. It works!

After updating to 10.6.1 I still had the problem. So called them (from Vietnam).

1. They had me look at the mail accounts. For some reason (SN upgrade?) had disconnected my.me account from being registered.

2. They had me create a new network connection profile called something other than automatic. And switch to the new profile. I erased automatic and left the new one.
(system preferences, networks, +, add new name)

More than 2 hours later my mail and browsers still work.

Having problems? Call Apple. It is free and included in your software upgrade for 90 days.

Doesn't work for me:-( After the upgrade not only my MBA cannot use the internet but none of the macbooks nor my iphone can use the internet connection. After modem reset everything ok for about a minute, then again complete freeze. Went back to 10.5.8 and everything is fine as before.

Seems like something causes complete freeze (congestion) of my internet connection (ADSL)...

This TOTALLY worked for me. I was getting all those "connection failed" messages and password errors after my neighbors got FIOS, and we tried everything to get me connected. These few steps got me online in two seconds. Awesome, thank you!

Thank you so much, it does work, but i skipped some steps, started at system preferences
and didnt see renew DHCP, so i turned it off and back on (the IPv4)

I have the same issue as the OP. I have no problem connecting to my wireless network at home, even with the Snow Leopard upgrade. The problem is with WiFi hotspots. My MBP connects to and recognizes the network. However, when I open my browser (Safari, Firefox), it cycles until it finally says,"connection failed" or "you are not connected to the internet." This ONLY started occurring when I upgraded to Snow Leopard.

I have an 15' Mac Book Pro, and a newer Mac Book 13', I upgrade the Mac Book Pro, to Snow Leopard and the Airport stops working well.
I upgrade it to 10.6.2, and still having problem. Today I change mi WiFi (D-Link) Router to an Apple Xpress. I'm writing this from the 13' Mac, connected to the Xpress. At Airport menu bar this machine detect like 6 neighbor wifis, and the 15' Mac, no one.
The only way that the 15' "sees" the Xpress is locating less than 3 feet of distance.

Is a nightmare, how can this be possible??? What happens Apple?? give us an answer!!!

it's most likely a simple keychain issue with your Mac, delete and start a fresh one