This looks a lot like glyph cache corruption. That's certainly not a real font or character set, but instead it is chopped up and mixed around pieces of the regular latin alphabet. You also have some random corruption in the form of those dashed lines on the right hand side.
This kind of bug is usually caused by your video card drivers, although it is not usually this severe. For example see the screenshots on this bug report:
It can also be caused by an overheating or failing video card or other hardware problems.