This is what I know so far:
Name resolution is only partially working. We have 6 VLANs associated with DHCP scopes. Users in some VLANs (IT, VPN, etc) are functioning normal using the same DNS/WINS/DHCP/Domain Controller servers as the other five.
Most users (not all) in the Employee and wireless VLANs can do an NSLOOKUP on FQDNs but they can’t ping by FQDN. They CAN ping by Netbios and IP.
Other users in the same VLANs are able to ping by FQDN.
The affected users' NICs in the employee/VPN VLANs are showing in Network settings as being part on the wireless VLAN but are getting their IP from the Employee VLAN.
DHCP scopes have not been changed except after the fact to take DC01 out of the mix due to issues with CPU saturation.
In DNS, there are no errors other than an old one which is not related.
WINS has no errors and appears to be functioning properly.
There are no entries in AD logs about broken trusts or anything other than our typical assortment of entries. There is nothing unusual in there.
I have no idea how to even troubleshoot this from this point. Please help.