Check your system date, especially the month and year, adjust if required.
The avast for Home program doesn't expire, the virus signature pattern updates do and you need to re-register for these updates even with the home version. This helps avast with the number of active users so they can ensure server support for updates, etc.
The registration for avast home VPS updates is 14 months so that would seem to be correct Feb 2006 to May 2007. So it may just be a computer hiccup.