I think the best you can do now is:

  1. uninstall avast and boot
  2. set up your email accounts just as avast does not exists.
    Test them, sendind an email to yourself.
  3. install avast 4.5 (instructions here: http://forum.avast.com/index.php?board=11;action=display;threadid=8044;start=0) and boot

Can you make a try and see if it’s ok? Thanks.