Clear the cache and the cookies from sites that cause problems. "Clear the Cache": * Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now" "Remove Cookies" from sites causing problems: * Tools > Options > Privacy > Cookies: "Show Cookies" See: *http://kb.mozillazine.org/Error_loading_websites ---- Do a malware check with some malware scanning programs.<br /> You need to scan with all programs because each program detects different malware.<br /> Make sure that you update each program to get the latest version of their databases before doing a scan.<br /><br /> *http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware *http://www.superantispyware.com/ - SuperAntispyware *http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page *http://www.safer-networking.org/en/index.html - Spybot Search & Destroy *http://www.lavasoft.com/products/ad_aware_free.php - Ad-Aware Free See also: *"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked