suddenly trusted sites are showing up as untrusted
Hi,
I am using a Macbook Pro 15 inch, OSX 10.9.5. I have been encountering situations where I can no longer go to certain encrypted sites without receiving a STOP warning message that the site is untrusted; using Angie's List as an example, I get a "Your Connection is not private" message (see attachment). If I click on the lock in the address line, I get information about Thawte saying that its certificate is not valid (see attachment). However, if I click on the certificate itself, it's good 'til 2016.
At first I assumed it was a browser issue (currently using Chrome); however, I tried the same thing in Safari and Firefox with similar results. In Safari, I inexplicably get a message that it's not a trusted certificate even though the certificate there shows as valid (see attachment). In Firefox, I just get a message that it's not encrypted. So, it's not a browser issue.
I have a PC at work, so tried going to angieslist.com on it; no problems whatsoever; it shows up with a green https://.
This has only been happening in the last few days since installing the regular system "security" update that automatically downloaded. When I look at "about this Mac," here's the OS detail: OS X 10.9.5 (13F1077)
Is this problem caused by the recent update? What do you suggest? (Is there a way to roll it back?) I'm concerned--how will I know when there really MIGHT BE a threat of hackers going after my information versus the bug that seem to have been introduced?
Thanks!
Diana
MacBook Pro (Retina, 15-inch, Late 2013), OS X Mavericks (10.9.5)