I have worked on this for literally HOURS. My keyboard was not typing the r letter. Tried the On-screen keyboard and another physical keyboard, and the same thing was happening. It was driving me nuts.
I started eliminating startup programs, and isolated this down to DOpus. Changed from the beta to the previous released version and it was still happening. As soon as I start DOpus, I can't type the letter r. Thought I was losing my mind with this one. I actually can't just close DOpus. I have to go into Task Manager and End Task. As soon as I do that, I can type the r again.
Apparently when I was trying to drag the tab the other day, I found something about making a hotkey to shift the tab right and created this but I didn't think it was working, and I did not delete it. So that was the problem, but I am curious as to how you know that the hotkey was probably the issue?
Pretty much every symptom you described pointed into that direction.
EDIT : To be a little more precise :
Opus is closed : R key is functionning perfectly
Opus is opened : R key seems to be somewhat "captured".
This looks like Opus is eating R key strokes, which is what a hotkey does. Since Opus lets you define different types of hotkeys (including system-wide) ... it was a good place to start looking into.