axelsena reported this behavior for his jabber.modevia.com server and I reproduced it locally. I can create an account at this server using Psi though.
Openfire 3.5.2, SparkWeb from trunk
I setup a local instance of Openfire 3.5.2 and I cannot reproduce the issue.
13:45:36.425 [INFO] INCOMING: <stream:features><starttls xmlns="urn:ietf:params:xml:ns:xmpp-tls"><required /></starttls><mechanisms xmlns="urn:ietf:params:xml:ns:xmpp-sasl"><mechanism>DIGEST-MD5</mechanism><mechanism>JIVE-SHAREDSECRET</mechanism><mechanism>PLAIN</mechanism><mechanism>ANONYMOUS</mechanism><mechanism>CRAM-MD5</mechanism></mechanisms></stream:features>
His server requires TLS, which SparkWeb currently doesn't support. We should add a specific error message for this case explaining that TLS is required and SparkWeb doesn't support it. Then the admin can choose to reconfigure his server to allow SparkWeb to connect without TLS.