Are you still able to run the Virtual Machine under Parallels? Looks like the pvs file is damaged. If you still have parallels 6, try to create a new Virtual Machine using the existing hdd file which contains the Windows OS.
Once you have done that try using the standalone convertor using the new pvs file.
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I havent tested this as i dont have parallels VM currently..
have you tried opening the hdd / pvs file directly using File > Open in Workstation itself?
