This happened to me before. The remedy was to power off the machine completely and remove the power cord for several minutes before attempting to start over. The cause of this was due to several quick resets causing HyperTransport bus sync floods resulting in I/O errors. What this means (I think) is that certain onboard controllers get their proverbial knickers-in-a-twist and like to complain until they've had time to recuperate from the stress of constantly being reset. I hope it works for you.

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