system
5
The same for me 2 days ago. I spent the day uninstalling and re-installing (after deep cleaning in safe mode) but no way. I just feel lucky because safe mode was working (I read someone had problem with this one, too brrrr). The sad truth is that Avast doesn’t like XP anymore 
I switched to Avira, let me know about Bitdefender’s free 2014 test 