Looks like you messed with the SSL Certificates of your phone then? It is VERY related. Does it happen to you with every https URL from the phone? In your N900: Settings (of the phone) -> Certificate Manager look for the Go Daddy Root Certificate Authoritiy - G2 (that's the one Whatsapp uses). Is it there? Does it say "Certificate not currently valid" or something? (it can't be it expires in the year 2037).