Hello Bunji and a big warm
from all of us at CF...
NTL dont block or filter any type of VPN connection. If you are getting time-outs when you are connected to the VPN then its most likely the VPN setup at the server end.
If however you are getting ping timeouts when you are trying to ping another ip address (IE Yahoo) then you have " use default gateway on remote network " switched on in the tcp/ip properties..
Can you post some screen-shots of the vpn connection blanking out any sensitive info and I will see if I can advise further
HTH