I'm having exactly the same problem as Oxa. My browser freezes, like clockwork, every 10 minutes, for about 5-10 seconds. The problem started sometime in August, cleared up for a few days to a week, then started again. I thought it might be either Online Armor or Avast. Turning off Online Armor did not fix the problem, but turning off Avast did. I updated Windows in August, but that was after the problem started. Aside from that, the only changes I've made to my software or system since mid-July are to the Avast engine and virus definitions, which I download manually daily.
Bottom line: Something changed in August. The only changes I made to my computer software were the Avast updates.
What else can I do to diagnose this problem?
Win XP SP3
Avast 7.0.1466
Online Armor 5.5.0.1557
Firefox 11.0
Windows Firewall: OFF
Windows Automatic Updates: OFF
Windows Task Manager: OFF
Avast cloud services: OFF
Avast automatic updates: OFF
Firefox automatic updates: OFF
Firefox addons automatic updates: OFF
Java update scheduler: OFF
All other automatic updates: OFF
Scanned with Malwarebytes and SuperAntiSpyware, and no malware found.