Remote VPN Setup Thru Cisco ASA

hiall.
i have a Cisco ASA5505 that I am using as my VPN concentrator.I previously had a public address on the public interface but I've had to set up the public interface with a private IP and NAT to a public IP on my internet router.
Now,my webvpn works fine that way but the ipsec-ra vpn does not connect from the clients.I've opened udp ports 500,4500 and protocol esp to the inside local(public interface)of the ASA5505 on my firewall(ASA5520) and set static NATs on the internet router to permit traffic to that host on those ports but it still doesn't work.
Any ideas anyone?