cron is trying to call another system (or the same one) to run
runq.  The authentication is failing.  It looks like cron and rexexec
are out of date.  Do you have a current version of
/sys/src/cmd/ip/rexexec.c and its corresponding binary installed?
Ditto with /sys/src/cmd/auth/cron.c?  I know that I updated one
before the other and that for a while they where out of sync.