sshd/telnetd stops responding under load

I get calcru messages from kernel built with sources 10 hours ago
cvsupped via cvsup12. When the system is under load, sshd and inetd
can get "calcru" messages and stop responding to any requests. Because
the machine is at a remote site, my original idea was to keep sshd and
inetd/telnetd running, so that when sshd freezes, I can telnet into
the machine and restart sshd (from a security point of view, this is a
bad thing, I know). But to my surprise, after sshd froze, telnetd
won't respond either. Connection was successful but no login prompt
appeared.

leafy_at_mail:~$ zh-telnet chihiro.mydomain.com
Trying 203.73.175.155...
Connected to chihiro.mydomain.com.
Escape character is '^]'.

And stops there. Same with ssh.

At this time,

1. any CGI script that httpd invokes will not run.
2. Static web pages are served normally (apache22)
3. ftpd responds and works correctly. (pureftpd)
4. Mail can be accepted but not processed properly

My guess is that anything related to spawning a new shell does not
work at this moment. That's why CGI, mail scanner (amavis,
spamassassin), telnetd session, sshd session won't come up. I won't be
able to get in front of the console for about 2 more months, but I can
get folks to reboot it for me so that I can get in before another
freeze. Any ideas what errors  to look for?

Cheers,

Jiawei Ye

--
"Without the userland, the kernel is useless."
               --inspired by The Tao of Programming