it's either 'reboot' or 'restart' (if it's stuck in the bootloader, there's also a 'help' command).
Settings you'll need are
- baud - 115200
- data bits - 8
- parity - N
- stop bits - 1
then fire up whatever terminal program you have (hyperterm, minicom, etc). It should connect and the router will respond. If hte router doesn't respond right away, hit enter a couple of times to "wake it up".