How are set your avast! services?
Start > Control Panel > Administrative Tools > Services

I suppose you have to have four avast! services:

C:\Program Files\Alwil Software\Avast4\ashServ.exe (avast! antivirus service)
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe (avast! Update Service)
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe (avast! Web Scanner service)
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe (avast! e-Mail Scanner service)

The two first of them should be Automatic loaded and the two last Manually loaded.