Odd - i'm getting a blank page here (Exception in thread "AWT-EventQueue-13" java.lang.NullPointerException at br.arca.morcego.Morcego.paint Morcego.java:325) but it works fine on the demo site: http://morcego.utopia.com.br/.
Sounds like an update might be possible?
This is in XP SP2, IE6, Sun Java 1.5
btw, Mac OS X is far more of a basket case on both sites so i have added this to the Morcego bug report list.
Hope this gets fixed or is fixable soon as it's a great toy!