Are you trying to use it on other distros/versions than the ones tested (FC13, RHEL5/CentOS5)?

There may be other conditions in those that cause the exploitation attempt to result in a session crash, rather than successful exploitation.

Also, the OffSec guys are notorious for making odd system adjustments. I wouldn't expect one exploit to work across the board (seriously though, what fun would that be? ).

Yeh agree with ajohnson it will be the OS you testing it again maybe it not using the same version or something similar to that.