If you have VPN Port Address Translation configured then you can just have 1 VPN Tunnel in the same time configured.
If you want to have more VPN Tunnels in the same time then you have to NAT this IPs.
See this post:http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1dd76646
search for my CCO in Post to find the answer from cisco.
The second problem is that the Peer VPN Device need to support Transparent NAT to send the ESP packets trough PAT UDP Port 4500. Also mentioned in the above post.
Have you enabled the " sysopt connection permit-ipsec" To enable globaly IPSEC if you have not opened ESP and IPSEC on the outside access-list.
Hope this helps
Patrick