Very wierd output problems

[Ulf Magnusson <ulfalizer@xxxxxxxxx>]

For some reason, output from programs that use printf no longer shows
up when they are run from ZSH. For example, the following C program
produces no output when run from ZSH:

#include <stdio.h>

int main() {
    printf("foo");
}

The ZSH builtin printf (that presumably uses the libc printf) doesn't
produce any output anymore either. The following is totally silent:

$ builtin printf Test%dTest 1000

Output via the function puts still shows up as it should.

All programs run as they should when invoked from Bash. I've tried
restarting ZSH and even the system, but the problem won't go away.
This is with ZSH 4.2.5, running on FreeBSD 5.4.

Ulf