Adding computers to domain--GPOs don't work

[Phyridean]

I've got a working Child domain, with GPOs enabled with loopback processing. When I add a machine to the child domain, it doesn't detect itself as being part of the group's it's part of...and it doesn't apply the machine policy, and thus, doesn't loop back to the user policy. It doesn't matter whether the computer has correct WINS or DNS addresses, or whether it was added interactively or by hand through the server. Any help? Please?

I can provide any information you think might be necessary to solve the problem.