The other day I was helping a client of mine who was having some problems getting a user setup as the local administrator on a laptop.
When I went to add the user, the "From this location:" option only showed the local computer name, not the domain.
The computer WAS on the domain, so what was going on?
Well it turned out that a new router had been put in on that subnet, and the DHCP on the router had started handing out IP addreses. Those IPs didn't have the DC as the DNS server, which is something that is needed in order to allow computers to figure out where company.local is really located.
After changing the DNS server to be the DC and not the router, everything worked as expected.