Hello Hans,
this was discussed a lot here in the forum and there appeared some reasons why that can happen (not on every Mac):
1) Don't type while the zoom is on. Try to type at 100% document view size.
2) If you are using inline objects (objects placed inside of text) try to work with contour text wrap, not with box wrap (the two image buttons at the bottom in the "Wrap" (Umbruch) inspector).
3) Don't use PostScript fonts but TrueType fonts, and be sure all used fonts are okay. You can check fonts with the Fontbook (Schriftsammlung) located in your Applications (Programme) folder.
Search for more in the forum and I am sure you will find a lot solutions. But not all solutions work for every Mac.