Starting last week, it seems cookies in my laptop stopped working. I'm unable to log on to any website, it just comes back to the login screen (Facebook) or says cookies need to be enabled (Gmail). I usually use Firefox and thought something was broken with it. But later I realized it has the same behavior in Chrome and IE.
Cookies are enabled and they work just fine in a site like this: http://www.html-kit.com/tools/cookietester/
We tried rebooting, there isn't an antivirus running, cleaning up the %TEMP% folder. I'm currently out of ideas on what to do next, except formatting.