The one other thing I ought to add, is that on the systems I see this,
cron is doing a lot of work - that is, root's crontab file would have
something to execute just about every minute (on the system currently 
experiencing the problem there are no other user crontab files, on the
one where it once occurred much more often there would have been a few
others as well, none of those requesting much work though).

kre