Issue with Task Scheduler launching a task

I have a task scheduled in my Windows 2008 R2 machine but it failed to trigger with the following error in the log (Event logs).

Error:

Task Scheduler failed to start "\Hyatt_International_Distribution" task for user "SAFFRON3\cb_admin". Additional Data: Error Value: 2147943645.

Task Scheduler failed to start Task Engine "" process due to an error occurring in "LUAIsElevatedToken" . Command="taskeng.exe" . Additional Data: Error Value: 2147943645.

The complete error is as below:

Log Name: Microsoft-Windows-TaskScheduler/Operational
Source: Microsoft-Windows-TaskScheduler
Date: 4/16/2012 9:59:59 AM
Event ID: 101
Task Category: Task Start Failed
Level: Error
Keywords:
User: SYSTEM
Computer: xyz
Description:
Task Scheduler failed to start "\Distribution" task for user "SAFFRON3\cb_admin". Additional Data: Error Value: 2147943645.
Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-TaskScheduler" Guid="{de7b24ea-73c8-4a09-985d-5bdadcfa9017}" />
    <EventID>101</EventID>
    <Version>0</Version>
    <Level>2</Level>
    <Task>101</Task>
    <Opcode>101</Opcode>
    <Keywords>0x8000000000000000</Keywords>
    <TimeCreated SystemTime="2012-04-16T14:59:59.950Z" />
    <EventRecordID>101476</EventRecordID>
    <Correlation />
    <Execution ProcessID="336" ThreadID="1216" />
    <Channel>Microsoft-Windows-TaskScheduler/Operational</Channel>
    <Computer>xyz</Computer>
    <Security UserID="S-1-5-18" />
  </System>
  <EventData Name="TaskStartFailedEvent">
    <Data Name="TaskName">\Distribution</Data>
    <Data Name="UserContext">SAFFRON3\cb_admin</Data>
    <Data Name="ResultCode">2147943645</Data>
  </EventData>
</Event>

The task is set as: Run s if user is logged in or not, With Highest privileges, Power: Start when on AC power, Allow task run on demand.

The task runs almost everyday, correctly, but failed yesterday. Any particular reason?