Hi, i have the same problem, i think it's the File Shield
it used to happen often even when i wasn't copying files or web browsing, if clicked on a folder it seemed like avast was scanning all its content, so i disabled "scan files at the opening" now it's better but "scan files at the saving" stills checked and in its settings i checked "scan all types of files". Maybe the problem comes from this last setting?
yersteday i created a 700mb iso file and after that Avastsvc.exe prevented me from using my computer for more than 1 hour!!
i don't want to stop File Shield (of course :p ), how can i limit the the % of cpu use?
sorry for my bad english.
Athlon 64 3200+ 2,2Ghz XP pro sp3
1Go DDR2 Kingston Firefox 3.6.3
ASRock K8NF4G-SATA2 Avast 5.5.545 Free edition
Comodo firewall 4.1.149672.916 Free edition