Aren't you running a 32 bits JVM?
Are you sure you have he 64bits .so?
Try using the one distributed.
We are using a 64 bit jvm passing in the -d64 option with Sun JDK 1.6.0_23
The native files came from this distribution
the hornetQ dLL (.so) has to match the same distribution. If you are using a newer distribution from SVN or what we have been working for the EAP, then you have to use the latest .so as well.