It took some experimenting, but now I have done this on 3 different systems and it works every time.
You will notice that with Comodo up and running, that the Nortel Contivity VPN client times out on retrieving banner.text. There is a document describing it here http://www.rz.uni-frankfurt.de/campusnetz/vpn/pdf/TT-Checking_Banner_text.pdf
To resolve this, click Security, then Network Monitor. You will now add 3 separate rules.
Action: Allow
Protocol: IP
Direction: In/Out
Source IP: Any (Or you can retrieve an IP from your systems administrator, but for us the IP changes)
Destination IP: Any
IP Details: Custom 17
Action: Allow
Protocol: IP
Direction: In/Out
Source IP: Any (Or you can retrieve an IP from your systems administrator, but for us the IP changes)
Destination IP: Any
IP Details: Custom 50
Action: Allow
Protocol: IP
Direction: In/Out
Source IP: Any (Or you can retrieve an IP from your systems administrator, but for us the IP changes)
Destination IP: Any
IP Details: Custom 51
Move these up above the bottom rule which should be Block
Fire up your Nortel Contivity VPN client get to work. 