Incremental Backup has failed

hello

i'm using acronis backup & recovery 11 virtual edition to backing up 5 virtual machines on a esxi server. there are agents on each virtual machine. everything worked fine, but since 1 week 2 backup's are going to fail every day.

here is the error message:

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Log Entry Details
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Type: Error
Date and time: 29.02.2012 16:51:54
Backup plan: [None]
Task: [None]
Managed entity type: [None]
Managed entity: [None]
Machine: ISMEsrv106.school.isme-sg.ch
Code: 20'250'627(0x1350003)
Module: 309
Owner: administrator
Message:
Command 'Running task 'Incremental backup' of backup plan 'Backup IsmeSrv106'' has failed.
Additional info:
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Error code: 3
Module: 309
LineInfo: 4a8728dc8a1c94f8
Fields: $module : C:\Program Files\Acronis\BackupAndRecovery\mms.exe
Message: Command 'Running task 'Incremental backup' of backup plan 'Backup IsmeSrv106'' has failed.
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Error code: 3002
Module: 329
LineInfo: 8234610504d1e287
Fields:
Message: Failed to run task '1' of backup plan 'E5AA6D9B-A6D7-091D-128B-0FC156A41394'.
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Error code: 92
Module: 9
LineInfo: d6e6b1a4069ca4f4
Fields:
Message: Failed to run now: task is already running.
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Acronis Knowledge Base: http://kb.acronis.com/errorcode/

Event code: 0x01350003+0x01490BBA+0x0009005C

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