Question on Pivoting and Run VNC

Hi guys

ive got a couple of questions probably easy solved.

im running 3 machines on vm player attempting to pivot between them

i have

bt 192.168.1.1
victim xp - 192.168.1.1 and 172.16.1.1
victim ubuntu - 172.16.1.2

ive attempted pivoting from bt to the ubuntu but bt reports unknown network. ive tried manually adding the routes and having them auto added but with no success. could this be because all the machines are running on vm player ?

also when i attempt run vnc on the victim xp machine i get

Error in script: NoMethodError undefined method `+' for nil:NilClass

ive googled both but im no further forward any hints would be great

cheers