Java Programming

Hello everyone! :D I'm currently working on something that can load 'configuration' (some kind of cache) via. XML files.
To do so I made a instance of the Object class:

    public static Object load(File file)
    {
        try
        {
            InputStream is = new GZIPInputStream(new FileInputStream(file));
            Object rv = xstream.fromXML(is);
            return rv;
        }
        catch (IOException ioe) {
            System.err.println(ioe.getMessage());
        }
        return null;
    }

And I have initialized the XStream class like this:

private final static XStream xstream = new XStream();

And yes I have imported this:

import com.thoughtworks.xstream.XStream;

But still I get this annoying error...
I store the xstream.jar in a folder named lib. (Together with some other JAR's like: xpp3, mina, hex-string and such things).
If you need more of my code just tell me and I'll post.