I have been battling this error for sometime now. We have recently built a Intel server with ESXi 4.0 running Windows Server Std. 2008 R2 SP1.
I started seeing this error shortly after starting backups with windows server backup to external 1TB HDD's. Error in System log:
Log Name: System
Date: 3/10/2011 12:56:45 PM
Event ID: 11
Task Category: None
The driver detected a controller error on \Device\Harddisk1\DR5.
<Provider Name="Disk" />
At first I though there was a problem with the virtual drive running windows. I later noticed w/o any USB drives plugged in that the errors stopped happening. I have tried combinations of adding the USB controller in ESXi many times, restarting removing USB controller, restarting adding USB controller etc...
The error only seems to post when the drive is ejected. Windows server backup formats the backup drive and hides it to stop overwriting of the backup jobs, and I thought that the way that windows partitions the drive might not talk well with ESXi, but even with normal drives attached by USB the error posts on eject.
I have searched everywhere for an answer to this System error with no success. I wish it related to hardware, but it doesn't matter what drive is plugged in via USB. On eject Sytem posts a Event ID 11 error almost without fail...
I look forward to your inputs...