Do you have WINS set up properly? In a full/complete AD setup, you may not need it, but by having a central WINS server set up, and all servers and workstations referencing it (through the DHCP properties) you can provide name resolution, at least for Window protocols.
Formerly, in your flat network, one of your servers probably WAS acting as a WINS server, as everything was reachable via broadcast messages. However, by routing, this method doesn’t work like it did without a little “help” to cross the broadcast domains. Registering with a consistent server for servers AND workstations will then allow name resolution.
Sounds to me that you dont have inter-VLAN routing set up properly. If your ENTIRE network uses the 172.16.x.x, and you throw in the 10.-w/e, the router needs to know it needs ot translate / route between the 2 subnets.
You could use either static routing from each site to the “main” network, as that would require so few statements, or your could enable a smaller dynamic routing protocol like RIPv2 to allow traffic to flow from the 172.16.x.x to the 10.x.x.x and vice versa…