I can't see anything wrong in the log file!? Can you please try to create a couple of files (text files, doc files, ...) within the VM. E.g. some files in your user's documents folder and maybe a new folder in the VM's c:\ root folder to see whether they are lost with the reboot too? This is to check whether this could be a Windows issue, where it - for whatever reason - reverts to the last known good configuration when rebooting.
André