Assuming youre on a PC, possible fixes are:
Go to Control Panel -> Internet Options -> Advanced -> Security and remove the tick from the position of "Check for server certificate relocation" and click Apply.
Or:
1. Click Start, click Run, type regsvr32 softpub.dll in the Open box, and then click OK. When you receive the message that the DllRegisterServer succeeded, click OK.
2. Click Start, click Run, type regsvr32 initpki.dll in the Open box, and then click OK. When you receive the message that the DllRegisterServer succeeded, click OK.
3. Click Start, click Run, type regsvr32 mssip32.dll in the Open box, and then click OK. When you receive the message that the DllRegisterServer succeeded, click OK.
4. Click Start, click Run, type regsvr32 wintrust.dll, click OK, and then click OK when you receive the message that the DllRegisterServer succeeded.
Or:
Download Microsoft's latest trusted root certificate update from here:
http://www.microsoft.com/downloads/...0e-ee7e-435e-99f8-20b44d4531b0&displaylang=en. Follow the wizard instructions carefully, because you need to download two executables, not just one.