Maybe stupid to suggest, but did you try the connection without firewalls ?

Anyway as you obviously know , ping is layer 3 in osi, so thats no guarantee the progs would work, so I'd start work my way up, with for.ex. try a dns resolve, an arp, a telnet , etc ...
Combine this with a networksniffer ...

That should at least give you more info ...

Hope this helps,