LC letter "b" often will not display

I've written MicroSoft and others about the failure of my screen to display the letter "b". Do note that it displayed in the title above but not in this body text! This goes on all day long and started over 6 months ago. No one seems to be able to provide an answer or solution. Uppercase "B's" display 9 out of 10 times, however. Any ideas about what fundamental corrupted machcine/software functions cause this would be greatly appreciated.