system freeze/hangs

Dear readers,

We have experienced some complete system freezes on DSS v6 Enterprise.
We susspect the USB key to be the cause of this problem due to the following entry in the critical_errors.log:
It's a while a go because we immediately moved to a new system with DSS 7.

Code:

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2014/05/29 22:38:43|reading directory #16443 offset 0
2014/05/29 22:38:43|unable to read inode block - inode=16674, block=32844
2014/05/29 22:38:43|nls_iso8859_1 nls_cp437 arcmsr uhci_hcd ohci_hcd ehci_hcd vfat fat aufs [last unloaded: ohci_hcd]<6>sd 3:0:0:0: [sda]
2014/05/29 22:38:43|Pid: 21193, comm: rsync Not tainted 2.6.27.39-oe64-00000-gc046424 #36
2014/05/29 22:38:43|Result: hostbyte=0x00 driverbyte=0x06
2014/05/29 22:38:43|
2014/05/29 22:38:43|Call Trace:
2014/05/29 22:38:43|[<ffffffff802367e4>] warn_on_slowpath+0x64/0xa0
2014/05/29 22:38:43|[<ffffffff8020b1a5>] __switch_to+0x315/0x380
2014/05/29 22:38:43|journal commit I/O error
2014/05/29 22:42:01|reading directory #16427 offset 0
2014/05/29 22:43:02|reading directory #16427 offset 0
2014/05/29 22:43:02|
2014/05/29 22:45:59|reading directory #16386 offset 0
2014/05/29 22:54:03|reading directory #16427 offset 0
2014/05/29 23:05:01|

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Our question is if this log entry really reveals that the problem is the USB key on which DSS is installed.
We could nod find any other problems in the logs or on the Areca SAS card.