Problem with windows server backup - incorrect function

I have a problem with a clients Windows Server 2008, trying to perform backup to an external hard disk. I always get the error 'Incorrect function' when about 99% complete.

I have tried a number of deviecs with the same result. Obviously I'm getting worried about getting a clean backup for the client.

Thanks in advance 

Phil R

ValeWest Ltd

Event log attached below

Log Name:      Microsoft-Windows-Backup

Source:        Microsoft-Windows-Backup

Date:          18/05/2009 12:40:29

Event ID:      5

Task Category: None

Level:         Error

Keywords:      

User:          SYSTEM

Computer:      TEBAYSERVER.M6Diesel.local

Description:

Backup started at '18/05/2009 11:24:44' failed with following error code '2147942401'.

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

  <System>

    <Provider Name="Microsoft-Windows-Backup" Guid="{1db28f2e-8f80-4027-8c5a-a11f7f10f62d}" />

    <EventID>5</EventID>

    <Version>0</Version>

    <Level>2</Level>

    <Task>0</Task>

    <Opcode>0</Opcode>

    <Keywords>0x4000000000000000</Keywords>

    <TimeCreated SystemTime="2009-05-18T11:40:29.375Z" />

    <EventRecordID>73</EventRecordID>

    <Correlation />

    <Execution ProcessID="9052" ThreadID="4500" />

    <Channel>Microsoft-Windows-Backup</Channel>

    <Computer>TEBAYSERVER.M6Diesel.local</Computer>

    <Security UserID="S-1-5-18" />

  </System>

  <EventData>

    <Data Name="BackupTemplateID">{748EE614-D7F7-4451-A543-0D4CDB4328CB}</Data>

    <Data Name="HRESULT">2147942401</Data>

    <Data Name="BackupState">12</Data>

    <Data Name="BackupTarget">F:</Data>

    <Data Name="NumOfVolumes">1</Data>

    <Data Name="BackupTime">2009-05-18T11:24:44.600Z</Data>

    <Data Name="HRESULT">2147942401</Data>

    <Data Name="VolumesInfo">&lt;VolumeInfo&gt;&lt;VolumeInfoItem Name="C:" OriginalAccessPath="C:" State="12" HResult="-2147024895" DetailedHResult="0" PreviousState="9" DataTransferred="23449042944" NumUnreadableBytes="0" TotalSize="23454909440" Flags="2" SSBTotalNoOfFiles="0" SSBTotalSizeOnDisk="0" SSBVhdSize="0"/&gt;&lt;/VolumeInfo&gt;</Data>

    <Data Name="DetailedHRESULT">0</Data>

    <Data Name="SourceSnapStartTime">2009-05-18T11:24:44.596Z</Data>

    <Data Name="SourceSnapEndTime">2009-05-18T11:25:32.571Z</Data>

    <Data Name="PrepareBackupStartTime">&lt;TimesList&gt;&lt;Time Time="2009-05-18T11:25:34.825Z" /&gt;&lt;/TimesList&gt;</Data>

    <Data Name="PrepareBackupEndTime">&lt;TimesList&gt;&lt;Time Time="2009-05-18T11:25:35.556Z" /&gt;&lt;/TimesList&gt;</Data>

    <Data Name="BackupWriteStartTime">&lt;TimesList&gt;&lt;Time Time="2009-05-18T11:25:35.556Z" /&gt;&lt;/TimesList&gt;</Data>

    <Data Name="BackupWriteEndTime">&lt;TimesList&gt;&lt;Time Time="2009-05-18T11:40:27.437Z" /&gt;&lt;/TimesList&gt;</Data>

    <Data Name="TargetSnapStartTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="TargetSnapEndTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="DVDFormatStartTime">&lt;TimesList&gt;&lt;/TimesList&gt;</Data>

    <Data Name="DVDFormatEndTime">&lt;TimesList&gt;&lt;/TimesList&gt;</Data>

    <Data Name="MediaVerifyStartTime">&lt;TimesList&gt;&lt;/TimesList&gt;</Data>

    <Data Name="MediaVerifyEndTime">&lt;TimesList&gt;&lt;/TimesList&gt;</Data>

    <Data Name="BackupPreviousState">9</Data>

    <Data Name="ComponentStatus">&lt;ComponentStatus&gt;&lt;/ComponentStatus&gt;</Data>

    <Data Name="SSBEnumerateStartTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="SSBEnumerateEndTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="SSBVhdCreationStartTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="SSBVhdCreationEndTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="SSBBackupStartTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="SSBBackupEndTime">1601-01-01T00:00:00.000Z</Data>

    <Data Name="SystemStateBackup">false</Data>

  </EventData>

</Event>