My vCenter ( 5.5 u2) currently resides on a Windows 2008 R2 virtual machine. The OS required some Windows updates which were successfully installed and rebooted. Upon the server restart, the vCenter service failed to start. In the Event Viewer I could see the following error:

 

The description for Event ID 1000 from source VMware VirtualCenter Server cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.

 

Looking at the log file (C:\ProgramData\VMware\VMware VirtualCenter\Logs\vpxd.log) I could see the following information:

 

06T16:13:29.933Z [04556 info ‘utilvpxdVdb’] [VpxdVdb::SetDBType] Logging in to DSN: VMware VirtualCenter with username jordansql
2017-02-06T16:13:31.943Z [04556 error ‘utilvpxdVdb’] [VpxdVdb::SetDBType]: Login failure – retrying once…
2017-02-06T16:13:31.943Z [04556 error ‘utilvpxdVdb’] [VpxdVdb::SetDBType] Failed to connect to database: .  Retry attempt: 1 …
2017-02-06T16:13:40.103Z [05620 warning ‘VpxProfiler’ opID=SWI-4431b782] VpxUtil_InvokeWithOpId [TotalTime] took 12000 ms
2017-02-06T16:13:41.944Z [04556 info ‘utilvpxdVdb’] [VpxdVdb::SetDBType] Logging in to DSN: VMware VirtualCenter with username jordansql
2017-02-06T16:13:43.953Z [04556 error ‘utilvpxdVdb’] [VpxdVdb::SetDBType] Encountered login error. Subsequent connection attempt failed: 28000
2017-02-06T16:13:43.954Z [04556 error ‘utilvpxdVdb’] [VpxdVdb::SetDBType] Aborting after 1 retries.
2017-02-06T16:13:43.954Z [04556 error ‘Default’] Error getting configuration info from the database
2017-02-06T16:13:43.954Z [04556 warning ‘vpxdvpxdMain’] Database not initialized. Nothing to unlock
2017-02-06T16:13:43.954Z [04556 info ‘Default’] Forcing shutdown of VMware VirtualCenter now
 

To fix the issue go to Administrative Tool – > Data Sources (ODBC) -> System DSN –> Congifure -> (ensure all the data is correct and retype password) -> Test DSN.