A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
We have experienced this problem and there is a known issue that you should check for.
If a user has the preview pane turned on in Outlook, Windows Explorer, or in (My) Computer the PowerPoint file is held open by a hidden version of PowerPoint. No changes will be saved to the presentation while the preview pane is enabled. You will not get an error message from PowerPoint and it will look like the file was opened and closed properly, however it was never actually opened for edit by "real" PowerPoint and all changes the user has made will be lost.
To fix this: Hide or disable the user's preview pane in these three programs and then the user should be able to make and save changes to the PowerPoint presentation once again. This does not seem to affect Word and Excel files when the preview pane is turned on in the tests that we have done. I have read that this is a problem both in Windows 7 (which we use) and in Vista when using PowerPoint 2007.
Note that some users may also get a "file locked" message or a message that the PowerPoint file can only be opened read-only. Again, turn of the preview panes and this should make the PowerPoint file usable again. The user should probably reboot their computer because I've noticed that some file-lock errors don't go away until there is a clean shutdown/restart sequence.
Andy