Just updated my Macbook Pro to Mountain Lion, but I am experiencing some problems with DNS resolving (i think). Some websites (for example Facebook, Google Adwords, Apple discussions) are not reachable through the browser (Google Chrome) most of the time. However if I ping them (using networking tools from OSX), they always respond. They never open in Chrome and sometimes in Safari and Firefox. The browsers tell me there is no or an empty response. I already checked the DNS servers (they are ok) and also flushes the DNS cache. I did not have this problem before upgrading. Can anybody help me out?