The normal question to ask in the circumstances you describe is 'What's different on my PC between yesterday and today?' Have you installed any new software or hardware? Have you downloaded anything off the net? Have you changed anything that might have security implications such as the settings in ZoneAlarm or Norton or the IE Zone? If nothings changed have a look at your ISP's web site to see if they have been having server problems. Come back to us if anything strikes you.