why sc query fails from one machine but works from another

Looks like your credential to access PRODSRV remotely doesn't have rights to query services.

Are the PRODSRV and Vista machines you're showing members of the same domain? How are you logged-on to each machine when you run this command?

It looks like a credential problem is all you're dealing with. Let us know re: the above and we'll work out how you need to be logged-on. You can probably get away with doing a "NET USE" to PRODSRV before you run the SC command and be home-free...

Edit: Before you run the SC, do the following:

NET USE \\PRODSRV\IPC$ /USER:<username you logon to PRODSRV with> <password you use on PRODSRV>

I'm suspecting that you're not using exactly the name username and password on the Vista machine and PRODSRV, but you are on PRODSRV and the other Windows 2003 box.