The file ld-linux.so.2 isn't being copied into the chrooted lib/ when new users are created. Without it, bash fails.
I'll investigate why this is and try to fix it. I assume I can add it to the create_chroot_env.sh script...
There are actually two libraries that bash requires which are not copied over for some reason. They ARE listed in ldd so I don't know why they don't copy.
As a temporary kludgy hack, I have added the following two lines to /root/ispconfig/scripts/shell/create_chroot_env.sh
cp /lib/ld-linux.so.2 ./lib/
cp lib/tls/libdl.so.2 ./lib/tls/