I just tested it and was not able to reproduce the issue. I have a macbook 15, with Yosemite 10.10.2, and had no issues with powerpoint 2011 in presentation mode. Pile, would you mind opening a support case so someone can get back to you on that ? Just send a quick message to firstname.lastname@example.org and we will get back to you in no time.
Thank you everyone for providing such great insight in to this issue.
Our team is aware of some situations that impact the quality of the content share while using PowerPoint. This is often caused by resource conflicts caused by PowerPoint and relatively new Application Specific Sharing.
Our testing as confirmed that it is recommended that the presenter select “Share Entire Screen” when using PowerPoint in ‘Presentation View’. This will prevent PowerPoint from improperly displaying on the Dual Monitor system.
There is also an option to manually configure PowerPoint to display in a “Window”, instead of taking up the entire screen. This will allow the presenter to share only the PowerPoint application, instead of entire screen. The following knowledge base article provides the steps needed to make this change both on a PC and Mac.
I hope that this information is helpful and have a great day!
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