Why does the Visual Studio editor show dots in blank spaces?

I have a strange bug in the Visual Studio text editor.
All my blank spaces are replaced by a “.”

public class Person
{
  int age;
}

looks like this

public..class..Person..........................
{..................
..int age;...................
}.....................

I reset the settings to default. Didn’t work.
I also re-installed VS2008. Still didn’t work.
What’s the error?