Sudden change in slide size on all SL projects/player color change by itself

Two days ago, I emailed someone a copy of this scene to assist me with some pause/play issues. He worked on the scene and fixed the issues and he emailed them back. When I opened them, they had this weird white space above and below the the main part of the slide.

I asked him what happened; he didn't know. However, he suggested I correct the issue in the master slide. But when I looked at the master slide, it's like the size of the canvas has changed, so I can't reside the background picture without distorting it. 

I never imported the file he sent me into my main project. However, I was redesigning the same scene in an older version of my project. When I completed the redesign, I exported that scene into its own file and saved it in three different places (hard drive, cloud and thumb drive). When I opened the newly saved file, it now has that same wonky border on all of the slides. I check all three files and the same thing has happened. Additionally, my main project now has the same wonky border on all of the slides.

If that's not enough, the player has inexplicably switched from white to black.

I've tried:

*Resizing the canvas. Didn't work.
*Closing the files and reopening. Didn't work.
*Closing and reopening SL. Didn't work.
*Installing SL updates. Didn't work.
*Restarting my computer. Didn't work.
*Rebooting my computer. Didn't work.

The only thing I can think to do is to uninstall and reinstall SL.

But before I do that, can anyone please look at my attachments and my SL file and identify the problem? Any suggestions to remedy this issue would be greatly appreciated. 

Thanks.