Syntax Error when loading property file after concatting several property files

[Elvis Napoleon]

I have three property files ( one for common properties, one for version
branch specific properties and one for release/build specific properties).
In build file I concat these files to one and then load properties.
I get Syntax error in property ${dest_root}\${version_pref
It should be ${dest_root}\${version_prefix} in some property but it seems to
be cut.

I am using ant-contrib and -lib option from commandline to load its jar.
Otherwise nothing else isn't in classpath.
OS is Microsoft Windows Server 2003 Enterprise Edition + SP2.
Ant version is 1.6.5 ( although same issue happens in 1.7.0 too).

    <property environment="env"/>
    <property name="current_config" value="build_${version}.properties"/>
    <property name="version_config" value="${version}.properties"/>
    <property name="common_config" value="common.properties"/>

    <tempfile property="myconfig"  prefix="mycurrent_${version}_"
suffix=".properties" destDir="${env.TEMP}"/>

    <concat destfile="${myconfig}" fixlastline="yes">
        <fileset file="${current_config}"/>
        <fileset file="${version_config}"/>
        <fileset file="${common_config}"/>
    </concat>

    <property file="${myconfig}"/>

I lost with this. Anybody got any clue?

Thank You,

Elvis N