When selecting a File to view in a Calendar Event, and wishing to return to the File list to select another file to view by clicking the "<" icon at the top-left of the frame, the screen goes grey and no links function. The only way to bring the screen back is to refresh the browser window, or to remain on the file and advance or back-up to the next file in sequence by selecting the ">" (Forward) or "<" (Reverse) links at the bottom of the screen. This does not appear to occur when selecting files in the Folder Directory tree.