When trying to log into a secure website the browser displays "cannot display webpage". This symptom is network wide. The issue happens intermittently. The only fix i have found is to reboot the machine. The problem goes away for about a half-hour than returns. The operating system is XP Professional service pack 2 and 3, internet explorer 6 thru 8. I tried installing Firefox and this fixes the problem for a moment and the problem returns. I tried all the fixes on Microsoft; reset browser, SFC.EXE protected files, lowered security setting, compatibilty mode. ECT.