RB450G Netinstall

Hi,
yesterday I used “search for updates” and “update” on a RB450G, the result is a bricked device in a boot-loop. I tried to Netinstall (hold reset button until yellow user led stops blinking, I also tried holding longer), but the device does not show up in the netinstall program. Can someone kindly point me to the correct procedure?

Unfortunately I do not have a serial cable at hand that fits the male connector on the RB450G.

Sry, my own mistake: Ethernet cable was broken … all OK now.