When you try to connect to 0.0.0.0 or 255.255.255.255 multiply times, you won't be able to connect to anything anymore after the 4th try (because of the limitation of 4 sockets per w5100)
This is because in EthernetClient.cpp there is at line 57:
if (!::connect(_sock, rawIPAddress(ip), port)) { _sock = MAX_SOCK_NUM; return 0; }

and the connect function in socket.cpp at line 82:
if ( ((addr[0] == 0xFF) && (addr[1] == 0xFF) && (addr[2] == 0xFF) && (addr[3] == 0xFF)) || ((addr[0] == 0x00) && (addr[1] == 0x00) && (addr[2] == 0x00) && (addr[3] == 0x00)) || (port == 0x00) ) return 0;

So, if the IP is 0.0.0.0 or 255.255.255.255 the socket will be opend, the status will be set to SnSR::INIT but the socket will not close after it fails because of the IP so it will be in INIT State forever.

To fix this simply add close(_sock) in the if statement:
if (!::connect(_sock, rawIPAddress(ip), port)) { close(_sock); _sock = MAX_SOCK_NUM; return 0; }

Greetings,
Spider