Ok, the result of log files after browsing different websites (avast, Microsoft, Windows update,...) is :
AshWebSv.log content :
06/04/2008 10:43:06,"","","",HTTP Status: -1,0,0,0,0,0,0,Unknown process,PID: 0,CON: 127.0.0.1:12080->127.0.0.1:1158 <--> :0->:0,SEQ: 0
AshWebSv.ws is empty
I'll try to use Norton removal tool and update this thread.
>> I just try Norton Removal Tool + repair and it still doesn't work. The only way is to disable WebShield. Does the log help ?