Check and see if setting the zoom to 100% keeps this from happening.
What you describe matches a known issue for certain zoom settings with Mac systems.
For More Information see: Edit Layout/Report in Pro 11 Screen turns to gray when using either of the scroll bars.
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip
PhilModJunk thanks for the info. It doesn't seem to happen at 100%. Unfortunately, this is too small to see, and 200% doesn't show enough. Do you know if this was fixed in version 12?
Hard to believe this wasn't caught in testing.
I searched for this quite a bit before posting. I was looking for "smear", guess I should have tried "blur".
I know that it's a lot of work, but you may need to resize the items on your layout so that they are large enough to see at 100%.
I don't own a mac so don't know if this problem persists--it only happens on some Mac systems, in FileMaker 12 or not.