As simple (actually probably very complex–too complex for me) as it sounds, the subject above is my problem. Avast internet security won’t open at all. It says I have 0 days left on my paid subscription; this is false! My renewal is not due until December 2013.
Do not know what to do. Please someone help me.
Thank you
Streim

try avast repair

controlpanel > ad/remove programs > avast > uninstall > repair option … wait a minute and reboot

any change?

Did as you suggested and still will not start on reboot.