Certificate expired

[eyeless666]

Hi I hope someone here can help! My computer (not the one I'm typing this on, this is my sisters) won't allow me to get into any of my online accounts that need a password or let me sign into MSN! It will however let me get access to the internet through Internet Explorer but still not any accounts ebay, paypal ect!
It says something about the security certificate expiring on all of them and that it reccommends I do not open any of them and to shut down the page!
I have just got rid of AVG and installed Norton because I had a Trojan Horse which Avg just wouldnt contain it, I no Norton isn't everyones choice but It works for me and I wont be changing it! Anyway I wondered if thisads anything to do with the problem?
Thankyou for reading my essay lol any help will be most appriciated!
Thankyou