Using SQL 2008 R2 on 64-bit Server 2008 R2 Box. Separate App Server. Randomly (daily) several users receive the following error while in the application: "Logon Failed. Details: ADO Error Code 0x80004005 Source: Microsoft OLE DB Provider for SQL ServerDescription: Login timeout expired SQL State: HYT00" Opinions vary from something misconfigured in SQL to a Network problem. Any ideas/solutions would be appreciated.
Generally this is caused by processes running slowly on your SQL Server instance causing things to slow down. It's very difficult to tell you what to do without a lot more information. My best suggestion would be for you to gather more metrics on your server. Look at the wait statistics (sys.dm_os_wait_stats), cpu use, I/O, etc. Understand the load running on your system and attempt to correlate that load to the moments when your errors are occurring.