Select the File menu
Select PowerPoint Options
Choose the Add-Ins section
At the bottom you should see a Manage: option with a drop down menu
Select the Disabled items option and click Go.
Select Presenter and then Enable
Close and restart PPT.
Keep an eye on the messages that come up if PPT crashes again, and if you see the "There was a problem with the Presetner plug-in, do you want to disable it?" dialog, say no.