I think your VNC session was using encryption (at least at some point). I can successfully extract the "hash" from your .pcap file and also crack it using JtR-jumbo.
Please use latest versions of JtR-jumbo and Ettercap (from GitHub) for best results
As you can see, things do work
Please use latest versions of JtR-jumbo and Ettercap (from GitHub) for best results
Code:
$ ettercap -Tq -r Chomsky-ThreepWood-VNC-NoEncryption.cap
ettercap 0.7.5.4 copyright 2001-2013 Ettercap Development Team
...
192.168.11.110-5901:$vnc$*a5d62a6cd58f41abe8785a4485811aac*248d3290ce533f028613f092f25834cf
...
$ cat hash # copy-pasted from above outut
192.168.11.110-5901:$vnc$*a5d62a6cd58f41abe8785a4485811aac*248d3290ce533f028613f092f25834cf
$ ../run/john hash
Loaded 1 password hash (VNC DES [32/64])
12345678 (192.168.11.110-5901)
As you can see, things do work