this is the response I got from support, which solved my issue:
1) Stop the runtime
2) Download the zip file attached on your RH6.2 and unzip it
3) Ask your system admin, to add to LD_LIBRARY_PATH or LDPATH (or both) the path <hyperic-sigar-1.6.4_HOME>/sigar-bin/lib, where <hyperic-sigar-1.6.4_HOME> is the directory were you unziped the zip file
4) Restart the runtime and check
It is like the native library used by java to get the information on the server is missing, it seems to be know on Red Hat:
http://stackoverflow.com/questions/12119569/java-lang-unsatisfiedlinkerror-org-hyperic-sigar-sigar-g...