sl_Send Fails Intermittently

sl_Send appears to be failing intermittently for me. I've tried a few different TCP server test programs as well as my own, and they all have the same results. Sometimes the server receives the data sent by sl_Send, and sometimes it receives NULL. There doesn't appear to be any pattern to success or failure; but if I call the function twice in a row, the 2nd attempt seems to work most of the time. I've included my full function below. I'm using the CC3100, and it is successfully connecting to my WiFi network. sl_Socket and sl_Connect seem to be working, and the server side sees the new client connection each time. However, sl_Send fails about half the time. Sometimes it returns -1 on failure, and sometimes it returns 20 (the number of bytes I'm sending) on a failure. Any ideas or suggestions would be appreciated.

int sendToServer ()
{
	SlSockAddrIn_t  addr;
	int addrSize = sizeof(SlSockAddrIn_t);
	int sockID;
	char msgBuf[20] = "EventMsg,12345678,2\n";
	int status;

	addr.sin_family = SL_AF_INET;
	addr.sin_port = sl_Htons(9898);
	addr.sin_addr.s_addr = sl_Htonl(SL_IPV4_VAL(192,168,2,117));

	/* Open a TCP socket with the server and connect with it. */
	sockID = sl_Socket(SL_AF_INET,SL_SOCK_STREAM, 0);

	status = sl_Connect(sockID, (SlSockAddr_t *)&addr, addrSize);

	/* Send the message buffer to the server */
	status = sl_Send(sockID, &msgBuf, 20, 0 );

	/* Close the socket with the server */
	sl_Close(sockID);

	return status;
}