I know many of you have had the issue and it has ruined your battlenet experience. I'm not very smart so I do not know why this works, but I saw the solution mentioned in an earlier thread and tailored it to my own computer.

The display glitch seems to be caused by a background app which provides an on screen indication of when you push either the number lock or caps lock keys. This probably also applies to people who have separate volume changing keys(I do but require function key to be held). This issue seem more likely to affect laptop users who often have this background app preloaded by Acer, Lenovo, etc.

For my Acer laptop I deleted all Acer bloatware(should have been done anyway) as I had a few apps left around which seemed useful(they weren't). If you are an Acer user, the process is QAAdmin. It is part of the Acer Quick Access Package.

I would imagine each manufacturer has their own version of this "feature" which makes the game unplayable. I hope this helps some people!