Do you have the latest <s>Aurora</s> <u>beta</u>, in case it was a glitch in the last build? ---- If you expand the technical details section of the error page, there should be some kind of explanation or code there. Can you copy/paste that into a reply? If it says something along the lines of "sec_error_unknown_issuer" this can indicate one of these situations: (1) Incomplete security software installation Some security suites include a feature to intercept and scan your web traffic, including secure connections. In order to do this, they must present a fake certificate to Firefox, which of course, Firefox rejects. Programs such as ESET and Kaspersky provide a way to either turn off this feature, or import a master certificate into Firefox so that Firefox will trust these programs. Does that sound relevant? (2) Malware Unfortunately, some malware also will intercept your secure connections. Often they can do this invisibly in IE and Chrome because they can inject certificates into the shared Windows certificate store. Because Firefox uses its own certificate file, you may get errors in Firefox that you do not get in IE and Chrome. To distinguish between these, it's helpful to inspect the "Issued by" section of one of the certificates from a site that works in IE but not Firefox. When you get the error page in Firefox, you can expand the "I understand the risks" section, and click the button to Add Exception. You don't need to actually save an exception to inspect the certificate, so you can cancel after viewing the certificate. Check the "Issued by" section to see what you find there. For example: * Name associated with your security software, such as ESET, BitDefender, Kaspersky, etc. * Sendori (indicates unwanted software from Sendori) * FiddlerRoot (indicates unwanted software named similarly to BrowserSafeguard, BrowserSafe, SafeGuard) * Something else What do you see?