2003 server domain problem

Greetings,
I'm learning about server 2003 and domain networks and I need help with next problem:
There is main network domain server,w2k3 enterprise,with three scopes added with same subnet mask-255.255.255.0.One scope's IP range begin with 192.168.0.1.Main server which is dhcp server also has 192.168.0.2 IP.Other two scopes IP range starts with 192.168.10.1 and 192.168.20.1.All workstations are XP domain clients.My problem is that I can't ping workstations from server in 192.168.10._ and 192.168.20._ IP group.Also can't perform Remote Desktop connection on them from server.But from clients in 192.168.0._ group I can normally ping all comps in all IP groups.
Thanks in advance!