Weird stuff not connecting to SQL server
IF, after trying everything in the known world, including updated the MDAC, try reading this knowledgebase article.http://support.microsoft.com/default.aspx?scid=kb;en-us;Q328306
What part of that that worked for me was deleting the key for the SQLSERVER instance under the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\ConnectTo\DSQUERY
Cheers.