help - g++ hangs during build

I am newbie to cpptask but familiar with ant; this is my first build.xml with cpptask, however, it mysteriously fails:

when fire the build with ant, the target contains "cc" task always hangs. I take a look from windows task manager, it seems g++ is hanging; if I end g++ process from the task manager, the build actually proceed and finish successfully - it does build what I intend to build.

My question is, what have I did wrong to cause this annoying behavior?

My ant version: 1.6.5
ant-contrib: 1.0b2
cpptask: 1.0b4
I am using mingw 3.9 with msys 1.0.10 on windowsXP with everything up-to-date;

following is my build.xml:
<?xml version="1.0"?>

<project name="test" default="buildAll">

<property name="base.dir" value="."/>
<property name="debug" value="true"/>
<property name="compiler" value="g++"/>
<property name="src.dir" location="${base.dir}/src"/>
<property name="test.dir" location="${base.dir}/test"/>
<property name="build.dir" location="build"/>
<property name="obj.dir" location="${build.dir}/obj"/>  
<property name="include.dir" location="${base.dir}/include"/>
<!-- specify api="unix" or api="win32" override platform default -->
<property name="api" value="default"/>

<taskdef resource="cpptasks.tasks"/>
<typedef resource="cpptasks.types"/>

<target name="usage">
    <echo message="Builds test"/>
    <echo message="Usage:"/>
    <echo message="ant -Dcompiler=[gcc | msvc ...]"/>
</target>

<target name="init">
    <mkdir dir="${build.dir}"/>
    <mkdir dir="${obj.dir}"/>
    <condition property="is-gcc">
        <or>
            <equals arg1="${compiler}" arg2="gcc"/>
            <equals arg1="${compiler}" arg2="g++"/>
        </or>
    </condition>
    <condition property="is-msvc">
        <or>
            <equals arg1="${compiler}" arg2="msvc"/>
        </or>
    </condition>
    <condition property="is-windows">
        <os family="windows"/>
    </condition>
    <condition property="is-win32">
        <or>
            <equals arg1="${api}" arg2="win32"/>
            <and>
                <equals arg1="${api}" arg2="default"/>
                <isset property="is-windows"/>
            </and>
        </or>
    </condition>
    <property environment="env"/>
    <!--  in case not set in environment, use an insignificant value -->
    <property name="env.LD_LIBRARY_PATH" value="."/>
    <property name="opencv.dir" value="${env.OPENCV_HOME}"/>
    <property name="opencv.lib.dir" value="${opencv.dir}/lib"/>  
</target>

<target name="clean">
    <delete dir="${build.dir}"/>
</target>

<target name="buildSegmentor" depends="init">
    <mkdir dir="${obj.dir}"/>
    <cc objdir="${obj.dir}"
        debug="${debug}"
        outtype="executable"
        exceptions="true"
        optimize="speed"
        outfile="${build.dir}/testSeg.exe">
        <includepath path="${opencv.dir}/cv/include"/>
        <includepath path="${opencv.dir}/cvaux/include"/>
        <includepath path="${opencv.dir}/cxcore/include"/>
        <includepath path="${opencv.dir}/otherlibs/highgui"/>
        <includepath path="${opencv.dir}/otherlibs/cvcam/include"/>
        <includepath path="${src.dir}/img"/>
        <compiler id="cp" name="${compiler}"/>     
        <fileset dir="${src.dir}/core" includes="*.cpp"/>
        <fileset dir="${src.dir}/img" includes="*.cpp"/>
        <fileset dir="${src.dir}/video" includes="*.cpp"/>
        <fileset dir="${test.dir}" includes="testSegmentor.cpp"/>
        <linker name="g++" if="is-gcc"/>     
        <libset dir="${opencv.lib.dir}" libs="cv, cvaux, cxcore, highgui"/>
        <defineset define="WIN32" if="is-win32"/>
    </cc>
</target>
   
<target name="buildOptiFlow" depends="init">
        <mkdir dir="${obj.dir}"/>
        <cc objdir="${obj.dir}"
            debug="${debug}"
            outtype="executable"
            exceptions="true"
            rtti="true"
            optimize="speed"
            outfile="${build.dir}/testOptiFlow.exe">
            <includepath path="${opencv.dir}/cv/include"/>
            <includepath path="${opencv.dir}/cvaux/include"/>
            <includepath path="${opencv.dir}/cxcore/include"/>
            <includepath path="${opencv.dir}/otherlibs/highgui"/>
            <includepath path="${opencv.dir}/otherlibs/cvcam/include"/>
            <includepath path="${src.dir}/img"/>
            <compiler id="cp" name="${compiler}"/>     
            <fileset dir="${src.dir}/core" includes="*.cpp"/>
            <fileset dir="${src.dir}/img" includes="*.cpp"/>
            <fileset dir="${src.dir}/video" includes="*.cpp"/>
            <fileset dir="${test.dir}" includes="testOpticalFlow.cpp"/>
            <linker name="g++" if="is-gcc"/>     
            <libset dir="${opencv.lib.dir}" libs="cv, cvaux, cxcore, highgui"/>
            <defineset define="WIN32" if="is-win32"/>
        </cc>
    </target>

<target name="buildAll" depends="buildSegmentor, buildOptiFlow"/>

</project>