I am trying to connect two sites with VPN 3000 concentrators and IPSec tunnel. I've done this several times with other clients sucessfully but not this time. I get this strange IKE error in phase 1."received an unencrypted packet when crypto active!!...

I just bought a new VPN 3005 and trying to create a lan-to-lan connection to one of our client who also has a same box. We managed to connect but I can ping them but they can't ping me. And nothing else seems work like FTP or Telnet either direction....