even if there isnt one slot left, you can use the one you still have 
(from logging in as root) to exec top, and send SIGSTOP to all the 
forkbomb processes, until youve got them all stopped, and then kill them off.. 
but what sounds strange is a single user being able to run more than 
MAXUPRC processes.. 

Isildur

On Tue, 18 Dec 2001, Greg A. Woods wrote:
> How can't root login?  If you mean on the console or other hard-wired
> terminal marked "secure" then there's definitely something wrong at a
> much deeper level than the process table being filled.  Logging in on
> such a tty normally does not require any new processes to be created.
> 'getty' execs 'login', which execs root's shell.  There's also always
> supposed to be one slot left that only root can use (though I haven't
> verified if this is still true on NetBSD).  What else was running as
> root on your system?  I.e. was anything else running as root which could
> have been forking new processes?