Unable to browse Internet on Mac OS X

Problem temporarily solved by running:

sudo killall mDNSResponder

As per this question: MacBook can't use internet, but nslookup and ping both work.

Still doesn't explain why this breaks down on sleep/resume though.

Perform all these steps, checking after each whether the problem is resolved.

1. Reboot your router

2. Reset your Mac's PRAM

3. In Terminal

   dscacheutil -flushcache
   

4. In System Preferences/Network, create a new (non-duplicate) network location, and configure it for your needs

5. In Terminal

   sudo launchctl unload /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist
   

6. Patch the 4 mDNS system files back to 10.6.4

   See https://discussions.apple.com/message/12683257#12683257

   There is even a package with the files.

   In this post https://discussions.apple.com/message/13346662#13346662 he says that he is using the patch on 10.6.7.

   Nevertheless, backup your 10.6.7 files first.

   And confirm successful replacement of each file.