What is the reason to use SQL auth and not Windows auth ?
Cross domain support for one, easier account maintenance for another. And I believe the VC setup guide suggest using a SQL account rather than Windows authentication as well. More security since you can ONLY administrate SQL not the Windows machine, no chance that a Windows account can blow up the server AND SQL.
It's MUCH easier to figure out authentication problems on SQL than involving domain membership and Windows local security issues. With Windows you have to contend with domain policy and other issues also.
So to elminate possible issues SQL authentication is better. However I do setup mixed mode, so I maintain the server with Windows, and VI has it's own authentication separately.
