Cannot connect to MS SQL server database? Database is running but for some reason cannot connect even through a data link?

Several articles are on the internet about this problem and there seems to be two common solutions.

Solution 1: Reinstall SQL server and/or download and reinstall latest version of Microsoft Data Access COmponents (MDAC). This may solve the problem, but doesn't seem to be the norm. The articles I found about this are:

This problem may arise because the MDAC on your machine is not properly installed or be ruined.
Install the correct version of MDAC again. You can download it from http://www.microsoft.com/downloads/details.aspx?FamilyID=6c050fe3-c795-4b7d-b037-185d0506396c&displaylang=en

My problem was resolved with a service patch to the SQL
Server software as well as the client install

Solution 2: The following was posted by several other KB's on the internet and may solve the problem:

http://support.microsoft.com/kb/232060/

One of the instructions was to disable anti-virus and disk security
software which I had not thought to do. I'm running Norton Firewall
which I've found in the past does tend to interfere with things if it
hasn't recognized a program yet so I disabled it and was finally able
to view the list. When I re-enabled the firewall, it recognized the
necessary components and everything works great now.

Data Link file - you can create a text file, then rename it from .TXT to .UDL, then double click the file and this gives you an easy way to test a database connection

To use the data link, double click the UDL file and click on the Provider tab.

1. Select the provider you are using, in this example I will be using "Microsoft OLE DB Provider for SQL server".

2. Click the Connection tab and then the down arrow under #1. Select or enter a server name. This is where you will get an enumerated error if you are having problems with your database as mentioned above - either download and reinstall, or shut down anti-virus programs, firewalls, etc. (might want to disconnect from the internet if you can).

3. In #2. you select which ever you need to authenticate your connection, I selected Use Windows NT Integrated security.

4. In #3. you select the database or catalog you want to connect to from the drop down and now you are ready to press the "Test Connection" button.