The AT-X command erases the sytem firmware & should not be used excpet when all else ha failed, however the system can be recovered
1: set the IP address of your manager pc to 192.168.42.2
2: edit the Bootp entry for your system a follows
Mac = the Mac address of your unit
IP Adress = 192.168.42.1
File name = ip401ng.bin
the unit dshould now download the correct fimware , use view/tftp log to monitor progress, this utility can also be used to obtain the mac address if unknown
Good luck