Could you please post your config. I would like to see your nat, global, and route statements at the minimum. In the mean time ensure you have the following
route (inside) 10.125.1.0 255.255.255.0 10.120.1.0 <-- routers ip address
nat (inside) 1 0 0
global (outside) 1 interface <-- or outside global subnet
or
route (inside) 10.125.1.0 255.255.255.0 10.120.1.0 <-- routers ip address
nat (inside) 1 10.125.1.0 255.255.255.0
nat (inside) 1 10.120.1.0 255.255.255.0
global (outside) 1 interface <-- or outside global subnet
If this doesnt work or you already have it specified, post your config and we can take a close look.
Regards,
Jami