What causer the "[Microsoft][ODBC SQL Server Driver]Communication link failure" error?

That could be caused by a lot of things....but mainly it usually shows the connection between the application and the database has been cut off. Check with your network folks to see if they have an outage for maintenance or something that time. Check with the server folks to see if any server updates/maintenance is happening then. Are the Domain Controllers being updated at that time? Are any updates/maintenance happening with the database at that time that could be killing connections?

-SQLBill

The following is part of my signature block and is only intended to be informational.
Posting advice: FAQ481-4875

Hi Bill. Thanks for your time. Users access the application through a terminal server, which sits in the data center that also houses the SQL server machine. So the connection to SQL Server is carried out from the terminal server. The terminal server is patched/updated once quarterly in a well-coordinated process. There is a file server however which is quite busy. A few programs runs from there to the SQL Server. The problem is the folks who own the database are not very responsive when it comes to troubleshooting...I will post here what we find out as we go along. A few users were disconnected last night around the same time...

MCP SQL Server 2000, MCTS SQL Server 2005, MCTS SQL Server 2008 (DBD, DBA), Training HOTT cert SQL Server 2012 Business Intelligence (SSIS, SSAS).