please help me with xwiki source build

I obtained the full xwiki source from svn repo: svn://svn.forge.objectweb.org/svnroot/xwiki/xwiki/trunk and also, got ANT configured in my machine. while building the source with "ant release" command, I get the following error. Can someone please help me fixing that? ... thnx. xwiki: [javac] Compiling 422 source files to D:\wiki\xwiki\build\classes [javac] D:\wiki\xwiki\src\main\java\com\xpn\xwiki\XWiki.java:86: cannot access org.exoplatform.container.RootContainer [javac] bad class file: D:\wiki\xwiki\lib\exo-platform.container-2.0.jar(org/exoplatform/container/RootContainer.class) [javac] class file has wrong version 49.0, should be 48.0 [javac] Please remove or make sure it appears in the correct subdirectory of the classpath. [javac] import org.exoplatform.container.RootContainer; [javac] ^ [javac] 1 error BUILD FAILED D:\wiki\xwiki\build.xml:236: Compile failed; see the compiler error output for details. Thanks, SQ