IP Communicator and CUVA - can't get video

Hi everybody! Firstly great to join a forum like this..hopefully the content and advice will grow as more people join up.
If anybody can help with the following issue I would be very appreciative!
I am using IP Communicator (2.0.1 and 2.1.2 tried) and CUVA 2.1.1.0. My system is a UC520 running 12.4(11)XW6. Internally with CUVA and 7941 handsets, video calling is fine. Externally over a Cisco VPN Client connection, IPC connects and registers fine but CUVA won't connect - I see a broken line between the camera and the communicator in the CUVA GUI. A packet trace doesn't reveal anything interesting nor does running various ephone debugs on the UC520.
Does anybody have any suggestions that might help me resolve this? Has anybody actually got IPC working correctly with CUVA and making video calls?
Many thanks in advance.

Comments
RE: IP Communicator and CUVA - can't get video
Did you get this working? I have multiple IPCC's working with CUVA in a local environment, but I haven't been able to get them working together on two machines. I have a broken link between Video Advantage and my IPCC. The ephone settings are identical on all phones.
My config contains the following:
telephony-service
video
service phone videoCapability 1
ephone 11
device-security-mode none
video
mac-address 001E.4FF0.8778
username "chris"
paging-dn 55
type CIPC
button 1:11
pin 12345
!
!
!
ephone 12
device-security-mode none
video
mac-address 001E.4FF0.8420
username "kristi"
paging-dn 36
type CIPC
button 1:12
pin 12345
!
Ephone 11 works, 12 does not.
If you resolved the issue, I'd appreciate your feedback.
Thanks much!!
hmm
Make sure that your DHCP pool has the correct ACL'S applied, allowing that data to be exchanged from your VLAN into your other subnet you set for the VPN pool..