MS PowerPoint not update after save the file

MS PowerPoint not update after save the file

Some users have reported that they make changes to their presentation and save; then when they re-open the presentation, the changes are not there.

One known cause for this:

• If you're using Windows Vista or Windows 7
• If the presentation is opened from Network ,Shared drive
• If the presentation is open in preview pane

          Changes to the file may not be saved, be sure to close the preview pane. 

Credit : http://www.pptfaq.com/FAQ00830_PowerPoint_2007_bugs_-_problems.htm