A recent Microsoft automatic update has added new security to IE8 that prevents some users from logging into the SLX Client. You will see a web page with "There is a problem with this website's security certificate" and the title bar will display "Certificate Error: Navigation Bolcked". We went into the Internet options and de-selected the following items "Check for server certification revocation" and "Check for publisher's certificate revocation". After restarting IE8 users were able to login without any issues.