starting with jrex

Hi all. 

Well I'm trying to take my first steps with jrex. I have installed 
mozilla 1.7.13 on a linux machine (ubuntu 5.10), and trying to execute 
the following code without success:

System.setProperty("jrex.gre.path","/usr/lib/mozilla");		
try {
	JRexFactory.getInstance().startEngine();
} catch (JRexException e) {
	e.printStackTrace();
}
JRexWindowManager winManager=(JRexWindowManager)JRexFactory.getInstance().
	getImplInstance(JRexFactory.WINDOW_MANAGER);
winManager.create(JRexWindowManager.TAB_MODE);
winManager.init(null);

it throws me the next on the console:

***************** JRexL inited *****************
***************** JREX-Logging disabled *****************
org.mozilla.jrex.exception.JRexException
	at org.mozilla.jrex.xpcom.JRexXPCOMImpl.startXPCOM(JRexXPCOMImpl.java:143)
	at org.mozilla.jrex.JRexFactory.startEngine(JRexFactory.java:222)
	at test.Seba.main(Seba.java:21)
Caused by: java.lang.UnsatisfiedLinkError: InitXPCOM
	at org.mozilla.jrex.xpcom.JRexXPCOMImpl.InitXPCOM(Native Method)
	at org.mozilla.jrex.xpcom.JRexXPCOMImpl.access$2(JRexXPCOMImpl.java:214)
	at org.mozilla.jrex.xpcom.JRexXPCOMImpl$1.run(JRexXPCOMImpl.java:173)
Exception in thread "main" java.lang.NullPointerException
	at test.Seba.main(Seba.java:28)

I think I'm not setting "jrex.gre.path" correctly. to which directory should I 
point it? What files should be there? Well, thank you in advance and excuse me 
for my poor english. 

P/D: I just have installed mozilla using linux/debian packages.