Just to let y'all know, if you use Firefox, and have a Gmail account, and you receive the error
You can fix it by going to "Edit menu -> Preferences -> Advanced tab -> Encryption subtab -> Verification button" and click the "Do not use OCSP for certificate validation" option. I've been having trouble for the last 2 weeks or so with my Gmail account for that very reason, and I found the solution here.
Error trying to validate certificate from mail.google.com using OCSP - server error.