Firefox acts like many sites have bad security certs, but often a simple reload can fix it...
I get the error,
Secure Connection Failed
An error occurred during a connection to www.facebook.com.
Peer's certificate has an invalid signature.
(Error code: sec_error_bad_signature)
This happens to facebook, gmail, google, craigslist, and sometimes it can be fixed with a refresh, but other times I need to restart windows or just walk away for ten minutes. It's intermittent, but annoying as hell...
This is clearly not because of the remote sites' certs, and my date/time is set correctly. I don't know what else to do other than add exceptions, but that is a bad option, as this happens nearly every time I try to load a new site...
Alla svar (1)
Which security software (firewall, anti-virus) do you have?
A possible cause is security software (firewall) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.
Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.
See: