Recently, I was facing this nagging issue pretty often.
A brief description of the problem:
When you try to do a quick preview of a Powerpoint presentation that came to you by mail, what happens quite often is that post the presentation, the mouse cursor dissappears.
There are many suggested ways to tide over this problem.
I have discovered a easy way out of it. In case this happens, just click on the ppt once more for another quick preview, and voila the cursor will reappear!!!