Subject: Re: can't fork but what's short?
To: None <sjg@zen.void.oz.au>
From: Charles M. Hannum <mycroft@ai.mit.edu>
List: current-users
Date: 04/09/1995 14:54:11 
You've told us neither the circumstances of the failure (i.e. what you
were running), nor the error presumably returned by fork().

At a guess, I'd say it returned EAGAIN, and you were trying to exceed
your soft process limit.