After Upgrading to Mac Os X 10.6 (SNOW LEOPARD) Internet is half-deading

Question

Yeah, i know this is a known topic, i'm stuck here 2h researching that.
I still couldn't find a fix on it.
I'm using facebook as a test site, because it isn't connecting to facebook anymore
But i'm still able to visit some sites, including here and Mail/MSN
Anyway i tried switching my DNS/DHCP/IP
I tried Upgrading (combo pack) to 10.6.5
Tried Fixing my permissions...
I just don't know what to do anymore,
This was my first disapointment with Apple,
and i'm really ****** off.
Other Information:
I checked on my modem status, and it seems "ATM" is not working properly...
I barely know what that means, but i need help!

Answer 1

Sounds like you have been through some of the posts. In summary here is what I have found in those posts. Two new ones are to Zap your Pram and reset your SMC (items 7 and 8). I can provide a longer description of any or all of these items if needed. In your case since you can get to some sites and not others I suggest searching these boards for that problem separate from a wifi issue.
Fixes known to have solved the problem to posters on this board
1. Verify that there are no interfering signals (other WiFi units and portable phones or microwave ovens). Change channels regardless as you can't “see” outside inference
2. Repair permissions – directions at http://support.apple.com/kb/ht1452.
3. If you have WEP security change your security to WPA or WPA2
4. Delete Keychain password for your wifi router or create a new password on your router
5. Network Prefs - Edit your wifi location (remove airport and re-install) OR create a completely new location.
6. Look for conflicting out of date or beta software (Peer Guardian, Parallels and VMFusion known issues, Sophos antivirus)
Thing that are recommended, not yet confirmed
7. Reset your PRAM– directions at http://support.apple.com/kb/ht1379.
8. Reset your SMC – directions at http://support.apple.com/kb/ht3964. This was suggested by Small Dog Tech Tails for many problems
9. Network Prefs - get a new DHCP lease
10. Network Prefs – disable Ipv6
11. Delete network preference files
12. Manually enter your ISP DNS IP addresses in Network Preference
13. Be sure your router firmware is up to date
14. Make sure there are no IP conflicts with other devices (change from standard DHCP to static or MAC assigned IP addresses).
15. See if you have country code issues with your router seeing a non US router header (using Console log file below)
Troubleshooting tips to help isolate the problem:
16. Grab a Console log and post the results here
17. Set up ping to continuously poll the router as a temporary fix
18. Create a new user and set up wifi for that user as a fresh start (this might be a solution as well)
19. Report bug to Apple - http://developer.apple.com/bugreporter/
You have to sign up to be a "developer" but it is free.