Cisco VPN vs Build-in VPN IPSec

Greetings,

I have been trying to use Chicken of VNC to connect to VNC Server running on Windows XP.

When I am in the office, I have no issue

When I am outside using VPN, Chicken of VNC freeze up, Microsoft Remote Desktop Connection is not working too.

To to test it, I installed Cisco VPN Client and connect. It then all work.

What's going on? Is there any other settings that I have to do?

Note: Using the build-in VPN, I am able to connect and access to file servers etc. But just not Remote desktop related service.

Thanks.
Matthew