Lost Connection To SQL 2000 After SQL 2005 Install

I've had a VB 6 / SQL Server 2000 app running in a network enviroment for a couple of years now at a client of mine. Recently, he upgraded to the latest version of Quickbooks which installed SQL Server 2005 on the server. Now there is SQL Server 2000 and 2005 residing on the same server. My VB app still runs on the server but will not run on other machines. I can ping the server from the other machines. Has SQL 2005 taken over the port I was using or maybe has new security features that won't let me access SQL 2000 using my current connection string? Here is my current connection string:
mstrConnStr = "Provider=SQLOLEDB.1;Persist Security Info=True;User ID=" & strServerLogin & ";Password=" & strServerPW & ";Initial Catalog=" & strDBName & ";Data Source=" & strServer.

Any help will be greatly appreciated.
Keith