Have you tried logging from another computer?
Have you tried to login Facebook with a few browsers such Internet Explorer, firefox, chrome:http://www.mozilla.com/en-US/firefox/http://www.google.com/chrome
1. Open Google Chrome browser.
2. Goto Tools > Options.
3. In the Google Chrome Options window, click “Reset to defaults” button on “under the hood” tab.
4. A pop-up will appear asking you confirm this action. Click “Reset to defaults” to revert back Google Chrome to default settings.