Question : Can only ping by FQDN between two different domains

I have two different sites connected via an IPSec LAN to LAN VPN.  I am able to browse shares, printers, terminal services etc but only by IP and FQDN.  At each site there is a dns server and that resolves names for the internet and LAN resources local to each site.  the DNS set up has forwarders pointing to each office DNS server, and I have added secondary zones which are copies of the others primary zones, but still I can only ping by FQDN.  eg ping server1 timesout, ping server1.domain.com gets a reply.

I have trawled through other solutions all day, if there is a solution out there I can't see it and I am sure it's not too big a problem to someone!

Thanks

Answer : Can only ping by FQDN between two different domains

A reverse lookup zone won't help you anything here. Your problem is that the client doesn't know which DNS suffixes it should check.
One way is to add the DNS suffix of the respective other domain on the clients in the Advanced settings of the TCP/IP properties (in the DNS tab). Make sure you add the client's own primary domain suffix in the list as first entry. Test this on a client before you roll it out.
Another possibility, if the host names in both domains are unique, is to use a WINS server for each site (and let the clients point to it) and let them replicate with each other.