It may indeed just be bad luck, let us know how it goes.
Thanks Hazelnut!
I'll chalk it up to a case of bad luck & bad timing. The drive didn't recover. However, on a positive note, Defraggler performed right through the failure and the system booted to the remaining drive after defrag completed. Headed to the store to get a replacement now.
One of our machines is running Windows XP x64 with all updates. It's disk configuration is 2x931 Gb RAID 1 with two partitions C: 50 Gb and D: 881 Gb. D: is an actively-used partition with about 20% free space. I ran Deffragler 1.09.138 for partition D: on Friday evening. After running about 1 day (as I can conclude from Event Viewer) machine stopped responding (though replied to ping) and started only after reboot on Monday. After reboting Intel Matrix Storage Console reports that it's checking RAID volume and fixing errors (have found 8 errors by now).
I've seen such scenario for this machine several times. I've never seen such errors without running Defraggler immediately before they apper. I'm sure these RAID errors are because of Defraggler. It would be great if these errors would be fixed.
I forgot to mention important fact that while Defraggler is running there is considerable workload on drive D: exists. It's one of the most important features we need.