It's not the same thing, but I have had to reinstall Informix from scratch and for some reason now it does dbimport very well, but if I try to dbexport a database it creates the directory and leaves it empty saying "Cannot make export directory".
Informix is IDS2000 9.21, Linux is RedHat 7 (out of the box - the problem was that upgrades to the glibc were installed and killed Informix). It is happening on two different boxes, but I have never seen it happen before. Any ideas? Perhaps some kind of missing package Informix is too stupid to complain about?