Windows Server 2003 2 network card + Windows Vista

Dear friends,

Dear friends,

I need help to know why pcs with Windows Vista can't connect to Windows
Server 2003 that has 2 network card. I am going to explain you the
infrastructure i need to create. Well, first of all, I have a server with
Windows Server 2003 Standard R2 OS, and I would like to create diferents
environments to develop software, like development and preproduction
environments. Nowadays, I haven't got more machines to install this
environments so I thought use Virtual PC 2007 to create this machines. Well,
I created a virtual machine for preproduction environment and i installed
Windows Server 2003 Standard R2 in this virtual machine. I installed 2
network cards in my physical server, one to use normally and other to use
with virtual PC. I configured all, and preproduction environment worked well.
I acceded correctly to web hosted in virtual machine and so on.
The problem appeared when pcs with Windows Vista tried to connect to SQL
Server 2005 installed in my physical server. PCs with Windows XP acceded well
by pcs with windows vista couldn't access. If I disable network card for
Virtual PC, all pcs connects well, but when I enable this network card again,
the problem is there again.

Somebody know how can i solve this problem??

Thank you very much.

Best regards