The issue resolved with a bit of looking into SQL Server help tools/books (also confirmed by QlikTech). Here it is for those who may be interested in it or came accross the same issue when using a named instance of SQL Server for QVPR:
SQL Server 2005
a. Open SQL Server Configuration Manager, and then expand SQL Server 2005 Network Configuration.
b. Click Protocols for InstanceName, and then double-click TCP/IP in the right panel. Note: InstanceName is a placeholder for the named instance of SQL Server 2005.
c. On the Protocol tab, notice the value of the Listen All item.
d. Click the IP Addresses tab:
- If the value of Listen All is yes, the TCP/IP port number for this instance of SQL Server 2005 is the value of the TCP Dynamic Ports item under IPAll.
- If the value of Listen All is no, the TCP/IP port number for this instance of SQL Server 2005 is the value of the TCP Dynamic Ports item for a specific IP address.
Note : If the value of the TCP Dynamic Ports item is not set, you must set it yourself. For more information about how to configure a server to listen on a specific TCP port, visit the following Microsoft Developer Network (MSDN) Web site: http://msdn2.microsoft.com/en-us/library/ms177440.aspx (http://msdn2.microsoft.com/en-us/library/ms177440.aspx)
e. Click OK.