My Magento installation started showing up the following error:
SSL Error: Invalid or self-signed sertificate
I looked around but nothing was helping and I am sure that the certificate was properly signed.
An hour later, it turns out that my /tmp directory was CHMODed to 777. Turning it back to 755 fixed the error.
Update:
If that doesn’t work – check out the answer suggested by Aleksey.