Does someone have the Remote Console? Hit BREAK (you probably already
have).
Were you at a ':' prompt when it hung or is ldev 20 running some
program?
Do SHOWJOB/SHOWPROC from some other terminal.
IIRC, a power-up with factory defaults sets ENQ/ACK enabled XON/XOFF
disabled which is great for a classic 3000 but the reverse of what you
want for an iX box. Be sure to check these and your baud rate after the
reset.