When trying to browse any website, such as nytimes.com, yahoo.com, etc, it take sometimes anywhere from 15s-120s for the page to display. For example, in Chrome, when I browse to nytimes.com, in the status bar, I see the message "waiting for css.nytimes.com" or "waiting for www.nytimes.com" for a long period of time.
This is happening at home (on VPN to my employer's network or off) as well as when I'm connected to my employer's network directly. The problem occurs on all browsers on my Mac [Chrome, Safari, Firefox] and the curl command line tool in Terminal.
This problem seems to be isolated to my Mac. For example, when I browse on my iPhone (or my Windows laptop or another Mac laptop) on my home network, performance is great. It's terrible on my Mac. So this is definitely an issue with my Mac (OS Mountain Lion). This seems to be isolated to HTTP/HTTPS and not all TCP traffic since I can use SSH/RDP w/o any issues.
Using Activity Monitor, I can see ample free RAM and CPU utilization is minimal. I noticed this problem a couple of weeks ago. A reboot clears it up and then after 2-3 days, browsing starts to slow down again. Some pages take minutes to appear (or some suddenly appear in a flash when I stop loading the page).
What can I do diagnose the cause?