I have 3-4 Photos in LR that in Library / Develop / Preview looks like this:
The File itself seems to be fine as it show properly in other tools.
Any idea how to fix this in LR?
Looks like an issue with not redrawing/refreshing the content of the display in general.
Could be a video card driver issue. Try updating the video driver of your computer by going to the manufacturer's site and get the latest driver directly from them.
ALso, Adobe just released LR 4.3, you may want to look into updating?
I've recently read about some video issues for Mac users with both LR and PS where weird behavior like this appears after doing things like moving or creating new windows and when using some plugins. Adobe knows about these video issues to some degree, but not sure what, if anything, became of the problem.