SQL Server 2012: Login failed for user. Reason: Failed to open the database configured in the login object Every so often, my SQL Server 2012 throws the following errors:
Error (likely related to the one below):

Source: spid99
The client was unable to reuse a session with SPID 99, which had been reset for connection pooling. The failure ID is 46. This error may have been caused by an earlier operation failing. Check the error logs for failed operations immediately before this error message.
Error: 18056, Severity: 20, State: 46.

Immediately before the error above (same timestamp):

Source: Logon
Login failed for user 'myUser'. Reason: Failed to open the database 'myDatabase' configured in the login object while revalidating the login on the connection.
Error: 18456, Severity: 14, State: 46.

My ASP.NET 4.5 website (consuming the DB) throws this error at the same time:

System.InvalidOperationException: Internal connection fatal error.

What may be causing these issues and how can I fix them?
We had the same issue. Several app servers were logging the same error. It turned out to be a bad SFP network port in the Hyper-V hosts frame. As soon as it was disabled all of the errors stopped immediately.