In some cases, you will need to reinstall MDAC 2.8 to correct connectivity issues. Windows XP with Service Pack 2 won't let you do this. But with this procedure you can reinstall MDAC.
The full text of this installation is found here: http://support.microsoft.com/kb/899861/en-us
Locate the mdac.inf file in c:\windows\inf
Right click and install
When prompted for a location, point to c:\windows\servicepackfiles\i386
Then when prompted for the XP cd, either load the cd or point to c:\i386