This is not my hint, but I'm reporting it here after seeing it posted elsewhere. Phillip Moore found a solution for occasional tcsh: no more processes and similar errors. Check his original post for details and the discussion.One modifies /etc/launchd.conf by adding this line:
limit maxproc 512 2048
A restart is then required to activate the new settings. Or find some other way to restart launchd, which I didn't feel comfortable doing. I'd run into this problem sometimes after opening multiple Terminals and running a bunch of shell scripts.
[robg adds: As Phillip notes on his page, you only need to do this if you've run into the 100 process limit before; there's no other reason to do it. Visit his page for more details on the settings...]

