Testing in a new User will quickly tell you if the problem is system wide or if it's your User's folder that contains the problem.
You can move some files into Shared folder for testing in the new User.
Your Hard Drive/Users/Shared
After you log into the new test User, drag from Shared (it actually copies) your files to the Desktop for testing.
Remember to drag it back from Shared when you log into your main User
CREATE A NEW USER
Go to System Preferences --> Create a New User in Users & Groups.
Switch to the New User by logging out/in under the Apple in the Menu bar.
Only default Apple apps will be in the Dock in the new User. Go to Applications to open PowerPoint or any other apps you might want to test.
Do you still see the issue?
If yes, then the problem is with your base files.
If no, then the problem is in your User's folder.
Options to fix in your User's folder.
Option 1) Reset permissions and ACLs. See this post
https://discussions.apple.com/thread/5275515?start=0&tstart=0
Option 2) Reset the PowerPoint files in your User's Library.
1 Move the PowerPoint Container and Office Group Container to a backup location
You can find these folders in the following locations:
• PowerPointContainer: ~/Library/Containers/com.microsoft.PowerPoint
• Office Group Container: ~/Library/Group Containers/UBF8T346G9.Office
2 Restart the machine
3. Empty the trash.
4. Open PowerPoint. Does it crash now.
Show User's Library
The User's Library folder is hidden by default. To unhide: Select the Finder in the Dock. Under Go in the Menu bar > hold down the Option key and you’ll see the Library.
Finding the User Library Folder
http://www.takecontrolbooks.com/resources/0167/site/chap11.html#FindingtheUserLibraryFolder
Macintosh HD Root folders
Applications
Library <NOT this library
System
Users > You > Library <this library