site-to-site VPN tunnel with remote VPN clients

Hi there - We have a situation where we have site to site VPN tunnel between
our 2811 router in the UK and our parents company's 3030 in the US. This
works well enough but the problem we are having is when we have have remote
VPN clients, connecting from home, into our 2811. When the site-to-site
tunnel is connected these remote vpn clients cannot access anything on the
internal 192.168.1.0 network that the 2811 is connected to, but as soon as
we stop the site-to-site tunnel, they can access everything.
If I connect to the 2811 withthe cisco vpn client, with the site-to-site
tunnel down and ping -t a 192 address continually its fine and i get replys
from the 192 address, but if i bring the tunnel up whilst i am running this
ping i suddenly start getting replys from the external ip address of the
router, if i bring the tunnel down again it reverts to replying from the 192
address.

Has anyone experienced this before? Let me know if you want me to post
config.

Thanks in advance!!!!