Application pool will not start

Everything was working fine yesterday when our team left the office. There was a server restart last night and now one of our encrypted site's app pool will not start.

We have found one error and two warnings:

Log Name:      System 
Source:        Microsoft-Windows-WAS
Date:          5/24/2012 7:29:48 AM
Event ID:      5059
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      
Description:
Application pool Kentico6 - WMSEncrypted has been disabled. Windows Process Activation          Service (WAS) encountered a failure when it started a worker process to serve the   application pool.

Log Name:      System
Source:        Microsoft-Windows-WAS
Date:          5/24/2012 7:29:48 AM
Event ID:      5057
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      
Description:
Application pool Kentico6 - WMSEncrypted has been disabled. Windows Process Activation  Service (WAS) did not create a worker process to serve the application pool because the  application pool identity is invalid.


Log Name:      System
Source:        Microsoft-Windows-WAS
Date:          5/24/2012 7:29:48 AM
Event ID:      5021
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      
Description:
The identity of application pool Kentico6 - WMSEncrypted is invalid. The user name or password that is specified for the identity may be incorrect, or the user may not have batch logon rights. If the identity is not corrected, the application pool will be disabled when the application pool receives its first request.  If batch logon rights are causing the problem, the identity in the IIS configuration store must be changed after rights have been granted before Windows Process Activation Service (WAS) can retry the logon. If the identity remains invalid after the first request for the application pool is processed, the application pool will be disabled. The data field contains the error number.

It looks like there is a problem with the Identity but we didn't change anything and it was working fine before. We checked the logs and there wasn't any suspicious activity. Any ideas what is causing the application pool to fail to start or what I could do to narrow the problem down?