mauropasse - This worked for me. The button I held down during power-up mode was apparently the WPS button:

Press press WPS button for more than 5 seconds to run web failsafe mode

WPS button is pressed for: 5 second(s)

WPS button was pressed for 5 seconds
HTTP server is starting for firmware update…

eth0 PHY0 Down Speed :10 Half duplex
eth0 PHY1 Down Speed :10 Half duplex
eth0 PHY2 Down Speed :10 Half duplex
eth0 PHY3 Down Speed :10 Half duplex
eth0 PHY4 up Speed :1000 Full duplex
NetOurEther = e4:95:6e:45:18:b0
HTTP server is starting at IP: 192.168.1.1
HTTP server is ready!