First, the process by which OS X checks the validity of root SSL certificates doesn't currently work behind an authenticating proxy, such as those used on some enterprise networks. If applicable, contact your network administrator. The proxy server may need to have its settings changed.
Disable the built-in application firewall, if it's in use. If you're running a third-party firewall such as “LittleSnitch” or “Hands Off,” disable that. Test.
In some versions of OS X, Parental Controls has a bug that prevents loading of secure websites. Turn it off.
Are the current date (including the year) and time shown on your system clock? If not, correct them and test.
Otherwise, launch the Activity Monitor application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Activity Monitor in the icon grid.
Select All Processes from the menu in the toolbar of the Activity Monitor window, if not already selected. Enter "ocspd" (without the quotes) in the "Filter" text field. Is a process with that name listed?
If not, select Go ▹ Go to Folder from the Finder menu bar. Into the text box that opens, copy the following line of text:
/var/db/crls
From the folder that opens, move these two files to the Trash:
crlcache.db
ocspcache.db
You’ll be prompted for your administrator password when you do this. Then reboot, empty the Trash, and try again.
