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?
The day you stop learning is the day you start becoming obsolete.