What version (6.0.1000 - be specific) Free AV
XP Pro SP3

Try an Avast Repair:

  • Go to Control Panel > Add/Remove programs > Avast Antivirus.
  • Scroll down and choose Repair function in the pop-up window.
  • Reboot. - Done

If this fails to fix your problems, please report back the answers to the above questions as well as the following:

What other security software do you currently have or did you have in the past on this machine including:

  • Antivirus (AV) Avast 6
  • Firewall (FW) PC Tools 7.0.0.111
  • Trial versions of AV, FW and other security programs none
  • Other security software Spybot

I did install Windows updte KB955759