What can it mean?
It sounds to me like something is messed up with the server or network configuration of your Yun. The internal operation of the Bridge actually uses local network sockets to communicate between the various processes, and if that configuration got corrupted, it could affect Bridge.put/get, and any of the special web server URLs that start with /arduino/, /data/, or /mailbox/.
Did you make any server or network/routing configuration changes?
At this point, maybe the best bet is to re-apply the latest system image, starting over again from scratch?