Question : One way traffic over a hardware VPN

Main Site:
Bonded T-1 (3MB)
Watchgurard Firewall (550e)
Small Business Server 2003 with Exchange 2003  Fully patched
35 workstations joined to domain

Site 2 (good working condition through hardware VPN)
Cable (6MBx1MB)
Watchguard Firewall(x10e-w)
5 workstations joined to main site domain

Site 3 (One way traffic through hardware VPN)
Cable (6MBx2MB)  Different company than 2nd site)
Watchguard Firewall  (x10e-w)
Small Business Server 2003  no Exchange 2003 fully patched
4 workstations joined to domain

I can get to the SBS server from site 3 through Outlook connected to exchange and also to file shares.
I cannot remote into a PC at site 3 from the main site.  I can, however, remote into a PC at the main site from site 3.
Also, I cannot ping from the main site to site 3.  

The reason for the ping failure alternates between two statements:

Reply from 192.168.0.1:  Destination host unreachable
Request timed out.
Reply from 192.168.0.1:  Destination host unreachable
Request timed out.

Any help would be greatly appreciated.

Answer : One way traffic over a hardware VPN

What subnets do you use locally at each of the sites?

Site A ->
Site B ->
Site C ->

Are any of them the same? and also the subnet masks?