This one's kind of weird, at least to me.
I've got MSSQL server 2k5 (STD) installed on Server 2k3 R2 SP2 (on account of some legacy software that doesn't yet support x64 or Server 2008), using Windows Authentication. It's configured to accept local or remote connections, over either TCP/IP (2) or Named Pipes (3). (I've tried disabling Named Pipes, didn't help.)
I can connect to it remotely from any of our SQL servers, and if I pull up the SQL SMS, I can connect if I punch in ".\instance" or [IP]\instance but not if I try [hostname]\instance or even [FQDN]\instance - I get the "No connection could be made because the target machine actively refused it" code 10061 TCP/IP error. Of course, nslookup returns the FQDN and proper ip of the server.
Incidentally, the SQL Server Agent also won't start, because it times out trying to connect to [hostname]\instance, which strikes me as particularly odd, given that the other four services are starting just fine, and their properties (under SQL Server Configuration Manager) say they're connecting to [hostname], and the option to change it is all greyed out. Only other thing I can think of to add is that the services are set up to start under a domain SA account, not that it should make a difference.
Any thoughts? (On either what's causing it, or how to correct it?)