1. The "nat 0" access-list should specify all local subnets, e.g:
nat (inside) 0 access-list nonat
access-list nonat permit ip
access-list nonat permit ip
2. The router or L3 switch behind the pix should have a route back to the vpn client pool subnet, e.g:
ip route
If these configs are already in place, then post your configs, I'm sure someone would be able to suggest a solution.
Regards,
Mustafa