Inserted images have an unwanted border or lines on one or more sides
You insert an image into PowerPoint or Word and notice that it has a border along one or more of the edges of the image. You know that the border is not part of the image itself. The border may not appear until after the file has been saved and re-opened.
The problem is caused by color profiles embedded in images. If you remove the color profile and re-insert the image, it should solve the problem.
For example, if you use Photoshop or a similar image editor, make sure that the "Embed ICC Profile" option isn't enabled. Open the problem image, disable this option, then save the image again and re-insert it into PowerPoint.
Another approach is to delete the problem image, then re-insert it. At this point it shouldn't have the unwanted border yet because you haven't saved and reopened the presentation. Then before you save, cut the image (press Ctrl+X) then use Paste Special, as PNG or JPG to put the image back into PowerPoint or Word. This removes the ICC profile and prevents the image from becoming corrupted when you save and reopen the presentation.
In theory, disabling compression might be enough to prevent the problem, but if you give the presentation to someone else and they don't also disable compression, the problem will occur.
Thanks to PowerPoint MVPs Echo Swinford and John Wilson for the fix. And to MVP/Moderator Kathy Jacobs for the nudge toward the FAQ.