my powerbook has started refusing to access a number of websites, instead displaying the message: safari can't open the page "..." because it couldn't establish a secure connection to the server "...".
Did you try to Safari Reset? Also, in Safari > Preferences > Security check to make sure accept cookies isn't set to never. If that both of those fail you could try creating a new account and seeing if the pages load in there.
I have this problem too. I live in Turkey and the problem - coincidentally or not - suddenly appeared a couple of days after the government introduced censorship.
Could it be connected? What does "couldn't establish a secure connection" actually mean?