Mystra Senizen

Can someone help me please? I'm trying to log into secondlife and this error is appearing. "Login Failed. Oftem this means that your computer's clock is set incorrectly. Please go to control panels and make sure the time and date. are set correctly. Also check thar your network and firewall are set up correctly. If you continue to receive this error, please to go to the support section of the secondLife.com web site and report the problem." Help me.