Brian from Backblaze here. Which browser was that? We often test with Mac/Windows and Safari/Chrome/IE/Netscape/Opera, etc. It all seems to work here. Did you tweak any browser settings or are you running stock?
Firefox cannot guarantee the safety of your data on www.backblaze.com because it uses SSLv3, a broken security protocol.
Advanced info: ssl_error_no_cypher_overlap