Please, activate logging in WebShield:

  1. Edit \data\avast4.ini file
  2. Find the section [WebScanner]
  3. Add the line:
    EnableLogging=1
  4. Restart Web Shield in XP (terminate and start again) or whole PC in case of Win98
  5. Browse (trying to access some webpages, specially the ones that bring trouble, etc.)

The log file are \data\log\ashwebsv.log and ashwebsv.ws.
They would be accessible when WebShield is terminated again.
Post them here or send by mail to rypacek (at) asw.cz
After that, disable the logging to avoid a big log file.