This mainly comes from hardware restriction; memory and MPU performance. In addition, when the viewer showing the first page or after opening a page, it also reads and extracts for next page to prepare to show and during the period it shows the hourglass icon. More simple/compact next page, less time you see the hourglass. You may fasten the time by converting a whole page into one image and put it on. In other case, more fonts used in a page, longer time it takes. Especially if you are using number of font in a first page of your presentation, you may not be able to see open the presentation file and just look hourglass icon. In this case please reduce the number of used font in page. In case you cannot operate the viewer for a long time, turn the lamp off once then turn it on again. You will be able to operate the viewer. However we recommend to review your presentation on your PC before trying to view it on the viewer. One or more pages of the presentation may have too complecated or use too many fonts to go with the viewer.