VPN to 515 pix through a cisco 677 router

[nille]

Hi,

I'm trying to connect to my office's pix from home through a cisco 677 router that use NAT. The cisco VPN software (v.3.5)works good, if I use a dial-up connection to my ISP, but nothing works if I use my DSL line through the cisco router. I can connect to the pix, but I can not do anything else: browse the internal network, browse the internet etc.. I can not turn the NAT off on the router, but I can open some ports. Can anybody tell me if is possible to make a vpn through the router's NAT?
Pix: 515 v. 6.1
Router: 677
VPN software: v.3.5

Regards,

Nils