I'm not commenting on any broker in particular, however some brokers maintain client funds in trusts and so forth that are not government guaranteed.
If the monies are held in a "segregated client account" it means nothing as far as the security of your account is concerned. It just means that the broker is not allowed to use those monies for his own purposes. But they do, and in the case of MFG (Man Financial Global) lose the money. It is illegal, but the money is gone.
Root around here. http://www.guaranteescheme.gov.au/qa/
