OK, finally, it appears that
<external-library-path dir="${env.PLAYERGLOBAL_HOME}">
<include name="playerglobal.swc"/>
</external-library-path>doesn't understand relative path. I.e. if env.PLAYERGLOBAL_HOME=../../anything then it will simply strip leading parent directories and combine the rest to the current directory. This looks more like Flex Ant task's bug rather then compiler bug though. Best. Oleg
