intel iMac running Snow Leopard 10.6.4. There are several user accounts on this computer, only one of which cannot access https sites. Safari eventually displays the message:

```
Safari can’t open the page [url goes here] because Safari can’t establish a secure connection to the server

```

Firefox and chrome also fail to display the pages, but they don't give an error message.

I have searched SuperUser, Apple Support, and Google, and I have found many posts but few solutions. I did try installing a new root certificate from Thawte as recommended in one of the posts, but that did not solve the problem.