Site-to-site vpn using cisco sdm over adsl

I am trying to configure a vpn on a cisco 1841 router with adsl wic to another 1841 using cisco sdm. I can get the tunnel to come up when I simulate it from my office to the site, but cannot get any of the sites to talk to each other. Has anybody come across this situation or similar before and has anyone got any ideas. I think it might be something to do with addressing scheme but ISP assures me everything is ok.