The javapacker ISS changes put the file association entries into HKEY_CLASSES_ROOT. Doing this results in an error half way through setup if you don't run the installer with admin privs (the default). The current installer setup runs just fine with lowest privs, so it'd be perhaps nicer to put the registry entries under HKEY_CURRENT_USER\SOFTWARE\Classes instead:

http://support.microsoft.com/kb/257592