the default directory, which is inside the virtual box folder I think.
Since your information is not giving me enough details to pinpoint the problem and the hard drive space is sufficient, then I recommend for you to look at the virtualbox debugging documents to pinpoint the issue at http://www.virtualbox.org/manual/ch12.html
Oh either that or Virtualbox has an IRC Channel specifically for users.. Didn't know if you saw it or not... #vbox
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