The Verisign certificates, commonly used as an intermediate certificate authority for Internet facing websites all expired in January of this year. This causes most browsers to display a warning when you first access the SSL-secured page.
If you get the error above, you probably have a server that doesn't have the newer intermediate certificates. I've had a few people ask me about this, so here are the links to Verisign's site to help.
http://searchsupport.verisign.com/content/kb/vs5781.html
https://www.verisign.com/support/site/caReplacement.html