The File Replication and backup log error:

My backup was failed last night and I have an unusual error in the Window Log. Currently my C: has nearly 7Gb of free space. It works fine for past few years. Any idea ?

Thanks


NT Backup Log
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Volume shadow copy creation: Attempt 1.
"Event Log Writer" has reported an error 0x800423f4. This is part of System State. The backup cannot continue.

Error returned while creating the volume shadow copy:800423f4
Aborting Backup.



Event Log
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Event Type:      Error
Event Source:      NtFrs
Event Category:      None
Event ID:      13570
Date:            11/19/2010
Time:            12:59:27 AM
User:            N/A
Computer:      HKG-DC02
Description:
The File Replication Service has detected that the volume hosting the path c: is low on disk space. Files may not replicate until disk space is  made available on this volume.  
 
The available space on the volume can be found by typing "dir /a c:".
 
For more information about managing space on a volume type "copy /?", "rename /?", "del /?", "rmdir /?", and "dir /?".

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.