Apple is giving me the same problem with earlier version of Safari. It stalls for MacPro whenever the wi-fi connection times out that require auto-join authentication again.
Once stalled, it will not make IP connections even after re-launch. It is waiting for auto-join from wi-fi, but wi-fi never throws up the auto-join window.
SMC reset does not fix this stalling problem. PRAM reset does not fix it. Nothing would fix it, except re-boot MacOSX.
Firefox doesn't have this problem. It will ask for auto-join and authenticate the wi-fi connection from the host. Even after Firefox had made authenticated the wi-fi connection, Safari still fail to make any internet connection, and keeps waiting, and stalls.
The only way to resurrect it is to re-boot MacOS.
It is frustrating, because Safari and all Apple's software that relies on auto-join to make internet connections will fail and stall, not just Safari. It is because auto-join thinks that the internet connection has already been made, and does not respond, even though the wi-fi host at the other end had timed out and disconnection the IP. Even after the user (client) re-authenticates and logs-in from the wi-fi host, and obtained the IP address from the wi-fi host, Safari still stall, latching on the stale de-authenticated IP connection, and does not realize the wi-fi host had terminated it.
The system diagnostic log shows that the airportd process has already been associated by autojoin, when it was not. That's the problem. It was still associated with the staled connection, never released it, and never re-establishes it because autojoin never detected that IP connection was obsolete.
This same bug occurred in prior version of Safari before the update. It was fixed by the software update on the MacPro. Now, the same bug creeps back in again.
Apple engineers, please go back to your old note, and fix this old bug that had been fixed in the previous version. Why bring back the old bug into the new version?