ernani,

   Your \config\database\db2.xml file should look something like the 
following. I have DB2 installed to c:\sqllib.


   <!-- 
=================================================================== -->
   <!-- ant properties/targets for IBM 
DB2                                   -->
   <!-- note: this is not a proper xml file (there is no root 
element)      -->
   <!--       it is intended to be imported from a *real* xml 
file          -->
   <!-- 
=================================================================== -->

   <property name="sqllib.home"                    value="C:/sqllib"/>
   <property name="database.script.file"           
value="${src.dir}/sql/${name}-db2.sql"/>
   <property name="database.driver.file"           
value="${sqllib.home}/java/db2java.zip"/>
   <property name="database.driver.classpath"      
value="${database.driver.file}"/>
   <property name="database.driver"                
value="COM.ibm.db2.jdbc.app.DB2Driver"/>
   <property name="database.url"                   
value="jdbc:db2:SAMPLE"/>
   <property name="database.userid"                value="userid"/>
   <property name="database.password"              value="password"/>
   <property name="database.schema"                value="CLEX"/>
   <property name="database.catalog"               value=""/>


Your build.xml should contain the following...

<!DOCTYPE project [
    <!ENTITY database SYSTEM "file:./config/database/db2.xml">
]>

See if those work for you

Cheers
Chris