I am in a new shop and the below error started to show up on 2/22 repeatedly until 3/7. 

```
Event Type: Error
Event Source:   SQLSERVERAGENT
Event Category: Alert Engine 
Event ID:   318
Description:
Unable to read local eventlog (reason: The event log file is corrupted).

Event Type: Information
Event Source:   SQLSERVERAGENT
Event Category: Alert Engine 
Event ID:   311
Date:       2/22/2011
Time:       6:52:44 AM
User:       N/A
Computer:   XXXXXXX
Description:
Attempting to re-open the local eventlog...

Event Type: Warning
Event Source:   SQLSERVERAGENT
Event Category: Alert Engine 
Event ID:   312
Description:
Successfully re-opened the local eventlog - NOTE: Some events may have been missed.

```

Then, the server shut down unexpectedly. The shutdown stopped the events. But, my concerns are: What was happening? Does anyone know what this means? More importantly, what kind of measures do we need to take to prevent this from happening?