long shot but I had the same thing the other day.
A N Other had edited /etc/security/user manually and left a non numric char in a field.
histsize = x20
changed to
histsize = 20
might be worth checking.
Mike
"Whenever I dwell for any length of time on my own shortcomings, they gradually begin to seem mild, harmless, rather engaging little things, not at all like the staring defects in other people's characters."