Snow Leopard doesn't allow me to access the internet

Do you use a proxy server for web access? That might not be configured correctly.

I am have exactly the same problem. Skype works fine, but browsers and mail are stuck. Mail gets the message "servers can't be contacted on port 993" - and I've tried other ports as well - and browsers just can't connect at all. Anybody have any ideas?

I am having the same problem any ideas?

I'm also experiencing this on both my MacBook Pro 17 and my iMac 24. No proxies, just a direct connection to the Internet.

DNS resolution works fine from Terminal and other applications appear to work flawlessly (Adium, Skype, VMware Fusion update notification for example) but Safari and Entourage (connecting to IMAPS) both intermittently fail?

It is as though the networking subsystem is toggling between states. "Network Diagnostics" reports Internet as working one moment, then the next it's failed and continuously cycles between these constantly. Same for the target "server". Terminal seems to suggest the interfaces are continuously up though so I'm not sure where the logic is being applied.

I'll have a better poke around though and see what I can find. It is exceptionally frustrating though!

Have you checked the DNS servers (try accessing something by numeric address)? Have you verified that your Mac firewall isn't blocking essential ports?

Just to add more detail, DNS settings are fine for both PTR (numeric / reverse) or A/CNAME (address) record lookups. All resolve perfectly fine and confirmed against another system which is working fine (sadly not running Snow Leopard).

On my MBP running Snow Leopard with the 'Network Diagnostics' application running, the "Internet" connection shows "up" (green) for 2 seconds, then "down" (red) for 4 seconds and cycling continuously between these two states. The application itself fails to complete the test, constantly alerting of "Network Change Detected" suggesting the network configuration has changed.

Being a UNIX systems engineer, I thought running a dtrace on both the 'Network Diagnostic' app and Safari would show up something but sadly highlighted nothing (I'm assuming Apple have disabled dtrace's ability to snoop system calls from these apps and others for whatever reason). I also wondered if the network interface (en0) was changing whilst the state is toggling between failed and passed in the 'Network Diagnostic' app but ifconfig constantly shows the interface in an "UP" state... I just did an unscientific "while true; do ifconfig en0 | grep mtu ; sleep 1 ; done" to display the interface state in a Terminal window on a regular basis.

I think the biggest irony is, it all works fine when browsing to the www.apple.com website - it's never "Safari can't find the server" on me yet! Ah well, I'll have another look at this tomorrow if I get time 🙂

i had the same problem and fixed it by manually resetting my location (system preferences -> network -> location).

OK, set my location manually now. Interestingly, the network configuration stated "unknown state" in its status. I've not seen that one before.

Anyhow, the new location has stopped the "Internet" from toggling from red to green and back in 'Network Diagnostics' but still the same issue with resolving from within Safari. Either get the "You are not connected to the Internet" or the "Safari can’t find the server". All works fine in FireFox though which is the only way I've been able to get to these discussion forums to date! 🙂

I've ruled out the firewall(s), turning off both the BSD firewall and the Apple GUI firewall temporarily. No change at all to the behaviour experienced.

I took the brave move and done a "Safari" -> "Reset Safari" and reset everything, cookies, cache ... the lot. Interestingly, now www.apple.com doesn't load at all or I get the HTML but the CSS does not render the page leaving it looking very mid-90s!

So, something definitely seems to be wrong with Safari in Snow Leopard?

Anyone else experiencing this issue?

OK, done a full PRAM and NVRAM reset now (http://support.apple.com/kb/HT1379?viewlocale=en_US) and that seemed to solve the issue... well, web pages were loading fine in Safari for a good 20 minutes or so before it stopped working again! sigh

I have got the same problem, tried everything. And the strange thing is that Skype works fine.

Any help is welcome!

I've found the solution, you'll have to empty the DNS server settings. That helped on my MAC, hope it does for you too.

Thanks Gorik for the pointer, it worked for me too.

For those wondering, open Terminal and use the command:
sudo dscacheutil -flushcache

Good it worked out for you. Can't help you with messenger sorry