My BM server's proxy is on a secondary address, x.x.x.1, while its primary
private address is x.x.x.5. I have DNS proxy running.

According to the Proxy Cache Server screen on the server, my DNS proxy is
listening on both the primary and secondary addresses, which I think is OK,
although no requests will come on the primary address.

I am pushing to the clients the secondary address, x.x.x.1, as the first DNS
server, and my Windows server as the second DNS server, and I'm trying to
troubleshoot long waits during the login process. It almost always seems to
work just fine, but if often takes quite a while. Brad, on the DNSDHCP
forum, thought the issue might be that the workstations were timing out
trying to register themselves with the x.x.x.1 address. The issue is
complicated (I think) by the fact that only half our users attach to the
domain - the others have no rights at all to the domain/Windows server and
therefore I don't want to push that address as the primary DNS.

Brad suggested I consider taking this issue up here on the BM side, so here
I am. Any suggestions appreciated. If it matters, I do not need any
clients to register their own machines with DNS.