Ha me & SirDice got sidetracked and hijacked post oops we are very naughty !
But please try my suggestion, i have a feeling DNS requests are not being passed from machine to router correctly/or vice versa and hard coding DNS servers may help.

Before changing them I'd like to see it tested with dig. There's some malware for OS-X that changes your DNS settings. This will also result in slow internet.

I'd like to make sure you don't have it :D

dig www.google.comLast login: Fri Oct 7 13:24:20 on console
MacBook-van-A-Tomano:~ atomano$ dig www.google.com

I changed the DNS settings according to your recommendation. Did not solve it - with that I had no internet connection at all.

That's all? That doesn't look right... It should produce something like this:
It's possible your network location got corrupted somehow, let's try this:

That should reset a few things.

; <<>> DiG 9.6.0-APPLE-P2 <<>> www.google.co
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35213
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.google.co. IN A

;; ANSWER SECTION:
www.google.co. 2925 IN CNAME www3.l.google.com.
www3.l.google.com. 217 IN A 74.125.79.100
www3.l.google.com. 217 IN A 74.125.79.101
www3.l.google.com. 217 IN A 74.125.79.102

;; Query time: 41 msec
;; SERVER: 192.168.1.254#53(192.168.1.254)
;; WHEN: Fri Oct 7 19:14:14 2011
;; MSG SIZE rcvd: 110

MacBook-van-A-Tomano:~ atomano$

MacBook-van-A-Tomano:~ atomano$ ipconfig set en1 BOOTP
ipconfig_set en1 BOOTP failed: permission denied
MacBook-van-A-Tomano:~ atomano$ ipconfig set en1 DHCP
ipconfig_set en1 DHCP failed: permission denied
MacBook-van-A-Tomano:~ atomano$

As root obviously...

I.e. you need to precede those commands with 'sudo':

sudo ipconfig set en1 BOOTP

Actually, I was rather annoyed that the SBS 2011 network configuration wizard doesn't even let you specify the domain extension (a change from SBS 2003 - not sure about SBS 2008). And yup, even with the chaos it causes MS stubbornly still defaults to .local!! Why couldn't they use .sbs or anything else?

If they are using DNS and Domain hosting from a company that MS has hooks with, like GoDaddy, SBS will automatically configure split DNS (assuming they are NATing a private IP space to external public space) so that internal machines DNS lookups go the right way, and external machines also go the right way.

If you don't let the wizard configure both your internal and external DNS records, it sets up everything to work off the external IP range only - so you have to create a new zone for your public DNS zone in the SBS DNS, the manually create the three or four records for internal lookups with your private IP addresses, including Exchange autoconfig record, to get everything to work right. It's not hard if you do some digging around, but annoying because overall the level and completeness of automation in SBS is pretty good overall. But then again, that's the difference between MS and Apple - Apple sweats the details and MS is willing to live with "basically good enough"...

I hate those types - if your wrong or clueless, your wrong or clueless - it doesn't matter who points it out to you :rolleyes:

Has anyone found a solution yet? I'm having the exact same problem on a MacBook Pro 4,1 on OS X 10.7.4. My wifi works fine everywhere except at one cafe, when it worked the very first time I went and hasn't since. I only started going there after I was already on Lion, so I don't know if this is a 10.7 problem or an older MBP problem.

All I know is that it's frustrating as hell, because the wifi works for everyone around me and for my iPhone.

Create a new Location for this cafe', and see if the new Location works.

Trevor

DNS Lookup Fail
 

I have also run into this issue on a customer's computer at work. Customer is very angry that we have not been able to fix it.

Would like to note, I've tried to create a new location and erase locations and rename locations, and it won't save any changes I make.

Can freely surf around using DNS addresses, but every link you click on references the name, not the dns address, so clicked links fail.

I know DHCP is working correctly, but DNS names won't resolve.

Been researching for a while, and find many reports of the same problem, but no fix. I'm out of ideas.

Chuckie Chuck.