How to use the Site to Site tunnel

We have established a Site to Site VPN tunnel. I can in our Cisco PIX 506E see, that there are one IKE and one IPSec active Tunnel. The first network have the address 192.168.1.0/24 and the remote have 172.24.64.0/24.
When i try to ping a computer on the remote site, the active IKE tunnels went up to two, but the active IPSec tunnels are still 1. I do not get ping responses and after a short while the IKE tunnels go down to one active again.

What can i do to get my communication to work ?

Best regards
Bo