Administrative log was the most informative:

[sqsrvres] CheckQueryProcessorAlive: sqlexecdirect failed

[sqsrvres] printODBCError: sqlstate = HYT00; native error = 0; message = [Microsoft][SQL Server Native Client 10.0]Query timeout expired

[sqsrvres] CheckQueryProcessorAlive: sqlexecdirect failed

[sqsrvres] printODBCError: sqlstate = 08S01; native error = 0; message = [Microsoft][SQL Server Native Client 10.0]The connection is no longer usable because the server failed to respond to a command cancellation for a previously executed statement in a timely manner. Possible causes include application deadlocks or the server being overloaded. Open a new connection and re-try the operation

System Log:

Cluster resource 'SQL Server' in clustered service or application 'SQL Server (MSSQLSERVER)' failed.

Application log:

[sqagtres] SvcStop: service did not stop; giving up.

[sqsrvres] CheckQueryProcessorAlive: sqlexecdirect failed

[sqsrvres] printODBCError: sqlstate = 08S01; native error = 40; message = [Microsoft][SQL Server Native Client 10.0]TCP Provider: The specified network name is no longer available.

Error4/30/2013 8:16:55 PMMSSQLSERVER19019Failover