I have been using avast! antivirus for the last 2-3 years now and it had been running flawlessly.
That was untill recently when avast! did a program update to 5.0.545. Whenever I start Windows, avast! displays it's presence in the system tray with a red cross on it. On opening the interface it says the system is unsecured with a big "fix now" button. Clicking the button causes the busy icon to appear but then...nothing. If I try and activate the individual shields manually for each one, a message appears saying "Unable to start the File System Shield! Shield unreachable."
I went into the Settings > Troubleshooting section and ticked the option that says "Load avast! services only after loading other system services." I did a restart but then looking at the option I ticked it is no longer ticked and doesn't seem to remember any changes I make.
This is a fully updated Windows XP SP3 system and avast! is running alongside the Comodo Firewall (only). I am truly stuck as to why it is suddenly playing up.