RD, as Ray pointed out, the most common cause is a loose strand of speaker wire causing a short, so even if they look okay carefully reconnect them to the surrounds. A second possibility is that an internal short has developed in a surround speaker, possibly from vibration. A receiver problem is a third possibility. If reconnecting the wires doesn't correct the situation, connect your main speakers temporarily as surrounds. If there's no problem it would indicate that a Bose surround is the cause; if there's still a shut-down, the receiver would be the suspect.
