VM (w/ windows vista) crashes when trying to access shared folders

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http://askubuntu.com – I'm with Maya (Linux Mint 13), fully updated. I have installed a legit copy of windows vista on Oracle VM vitualbox, since I have the need of some programs only compatible (in an easy way) with windows. Problem: The first time I try to open a specific file (filename.docx) with microsoft office (any of the programs and file extensions like .doc;.docx;.ppt;.xlsx etc...) which is stored on a folder that is shared shared through the VM. The result is always that the machine crashes and reboots. Afterwards I see a new file in the same folder named "~$filename.docx" and I can now open "filename.doc (HowTos)