I had a similar problem here, the first one we changed thePSU and all worked ok, then we had a similar fault at another site and once again changed the power supplies and all worked ok, strange thing was that the error log showed AC power down, but the MTC console connection didn't disconnect. Checked both PSU serial numbers and they were both manafactured within a 3 month period( 2008)Sent them both to tech support and they are both being replaced out of Japan. Both were M power supplies and apparentltly there was an issue with some components.