Problem with Nat Config using ipsec in pix 501

[franspain]

I have a vpn peer to peer connected in a pix and also have a Nat config to provide access to my internal hosts to the external. My problem is that I have it already configured but the hosts can't ping any external host. They cannot ping but can reach web, ftp, ...

Does anybody know which could be the problem?

Thanks

[tvorhauer]

access-list acl_inbound permit icmp any any echo-reply

This will permit icmp replies when initiated from the inside.