I have found a bug tracking tool: Flyspray (actually it is version: 0.97 -> for joomla it is "Mambo Edition 1.0.1" )
This tool is even easier to configure and use than the vmware bugzilla which I wrote once about (reason was: sometimes the vmware made problems because of some network card problems and I could not use bugzilla -> thread is in: groups.google.com/group/comp.software-eng/browse_frm/thread/5ad2b594c1898b7c/44e5ed7dd4000988?
lnk=st&q=erkan+vmware+bugzilla&rnum=1#44e5ed7dd4000988 )
ok, it has not so much options like mantis or bugzilla, but hey, it works and is only dependent on the real internet-problems, if there are any (sorry for VMWare here )