At last my hardened uclibc Asterisk CD is booting again. But somehow Asterisk refuse to start with the default init script and it will only successfully start if I had the -v option. So I had to do this small workaround in the init script:
--- etc/init.d/asterisk.orig 2007-10-04 21:44:07.000000000 +0200
+++ etc/init.d/asterisk 2007-10-04 21:44:36.000000000 +0200
@@ -191,5 +191,5 @@
if [ "$(echo ${ASTERISK_WRAPPER} | tr '[:upper:]' '[:lower:]')" != "yes" ]; then
start-stop-daemon --start --exec /usr/sbin/asterisk \
- ${OPTS} -- ${ASTERISK_OPTS}
+ ${OPTS} -- ${ASTERISK_OPTS} -v 2>&1 > /dev/null &
result=$?
else

If I don't add the -v switch it seems like Asterisk just hangs after spawning only a few threads.