It happened once. 2GB of wasted disk space is not a joke ut part file wasn't created. But ut had written whole files. Only few hours later It made a part file for another pieces. try this Pref.->General->preallocate files - checked (after restart ut) also post your disk cache settings 'Preferences->General->Pre-allocate all files' was already checked. Disk Cache settings screenshot: http://img197.imageshack.us/img197/6789/diskcache.jpg