Configuration: I'm running stock Fedora 12 with the ant that Fedora ships:
<project name="antlibtest" default="doEcho">
<echo message="Hello World!"/>
This seems to be the problem described in Bug 490542 (that applies to Fedora 12 too according to the last comment). Sadly, the bug is still in a NEW state so I don't think it will be solved in a near future.
Regarding ANT_HOME, doesn't
/etc/ant.conf set it to
/usr/share/ant as explained here? This may be outdated but I can't check it (and I don't really get how this should be setup on Fedora).