Windows vista connect to SQL server 2005

Hi!

The SQL server 2005 is installed on a windows 2003 DC.
I also have a 2003 workstation (on the domain) for test and i have installed SQL 2005 and msde 2000.

I’m using windows vista SP1 32/64 machines to connect to sql server.

I cannot connect to all the SQL 2005 instances, from the vista machines.
(the management studio express – error: 26 cannot find server/instance)
(OSQL error- 53 cannot find path)

I can connect to the MSDE 2000 from vista.
i can connect to SQL 2005 (and msde 2000) from XP.

it’s not the firewall, the DNS its OK, the path, server and instance names are ok.

I really don?t know what to do to find the source of the problem.

thanks for the help.

Inneed4help