I have lost the icon from my toolbar.
Which is your Windows? 98, Me, XP?
Do you use any other antivirus in your computer?
Can you try to repair your installation?
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove. Then choose Repair function in the popup window (Repair). You must be connected to the internet while repairing.
If this does not help, can you uninstall / boot / install / boot again?
Does this mean that my computer is no longer protected?
If you click Ctrl+Alt+Del can you see ashServ.exe running?
If not, the providers are not running and you're not protected. Otherwise, just the icon problem that could be solved repairing avast! installation as above.