Volume Shadow Copy: Maximum number of snapshots reached

I'm trying to run an incremental backup job using Cobain 9 on an XP Pro PC setup as a server (I know but it's what we're working with).
When Cobain tried to create the VSC, I get a VSS error.  Here's from last night's job:

    7/22/2010 3:01:06 AM Changing the backup type for "Daily Backup" to Full (Backup number 9)
    7/22/2010 3:01:06 AM Initializing the Volume Shadow Copy. Wait...
ERR 7/22/2010 3:01:07 AM Volume Shadow Copy error on "AddToSnapshotSet": Maximum number of snapshots reached
    7/22/2010 3:01:07 AM Couldn't use the Volume Shadow Service. Proceeding with a direct copy
    7/22/2010 3:01:07 AM The destination directory "F:\***** Shared 2010-07-22 03;01;07" doesn't exist. Trying to create it
    7/22/2010 3:01:07 AM The destination directory "F:\***** Shared 2010-07-22 03;01;07" has been successfully created
    7/22/2010 3:01:07 AM Copying the directory "D:\***** Shared" to "F:\***** Shared 2010-07-22 03;01;07"
    7/22/2010 3:29:29 AM The directory "D:\***** Shared" was copied to "F:\***** Shared 2010-07-22 03;01;07". 40646 file(s) were processed
    7/22/2010 3:29:29 AM The destination directory "F:\Workstation Backup 2010-07-22 03;29;29" doesn't exist. Trying to create it
    7/22/2010 3:29:29 AM The destination directory "F:\Workstation Backup 2010-07-22 03;29;29" has been successfully created
    7/22/2010 3:29:29 AM Copying the directory "D:\Workstation Backup" to "F:\Workstation Backup 2010-07-22 03;29;29"
    7/22/2010 3:45:46 AM The directory "D:\Workstation Backup" was copied to "F:\Workstation Backup 2010-07-22 03;29;29". 24296 file(s) were processed
ERR 7/22/2010 3:45:46 AM Volume Shadow Copy error on "SetBackupSucceeded": The Volume Shadow Copy backup doesn't exist
    7/22/2010 3:45:46 AM **** Backup for "Daily Backup" ended. 64942 file(s) were backed up. (Elapsed time: 0 hour(s), 44 minute(s), 39 second(s)) ****

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The source drive is 52.2GB total, with 39.7GB free
The destination ext drive is 465GB total, with 103GB free.

There are no other applications using the VSS service when this backup runs, but they do also use MOZY to backup as well, and I'm not sure if it uses the VSS service when the Cobain job tried to run.  If it does, it may be the issue.
I need to know what's causing the VSC to fail.  Disk space?
Thanks.