You are not the only one with this problem see:- http://blog.sqlauthority.com/2009/05/21/sql-server-fix-error-provider-named-pipes-provider-error-40-could-not-open-a-connection-to-sql-server-microsoft-sql-server-error/

>In my web application I routinely spawn a separate .exe to process long requests asynchronously. For some reason, this process occasionally fails with the error message:
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>Connectivity error: [Microsoft][SQL Server Native Client 10.0]Named Pipes Provider: Could not open a connection to SQL Server [1326]. [1526:1326]
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>This is my connection string:
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>driver={SQL Server Native Client 10.0};server=TEST1;Failover_Partner=TEST2;database=testdatabase;uid=myusername;pwd=mypassword;
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>There are currently 4 web servers in load balanced mode hitting the mirrored database. This error message pops up in my error logs a dozen or so times a day but the process successfully runs at least a few hundred times a day. The failure is very intermittent with no discernible rhyme or reason. It happens on different servers. It happens at different times of the day. It happens during light load. It happens during heavy load.
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>Any ideas?