Do you mean that say, the 2801 has a 10.1.1.1 address on its outside interface, this is NAT'd at some point on another device to 200.1.1.1, and the VPN client is configured to conenct to 200.1.1.1?
If so that is fine, as long as it is a one-to-one NAT translation and not a PAT (one-to-many) translation.