Have you run any security scan for infections?
When you run these scans it will be most effective if you run them in Safe Mode.
Just for grins try the following and see if it corrects the problem.
The instructions came from this
1. Control Panel | Regional and Language Options applet | Languages tab | Details button, which gets you to the "Text Services and Input Languages" dialog.
2. On that page "Add" a second input language (you don't have to make it the default). The two (or more) I usually have installed are "English (Canada) - US" and "English (United States) - US". Once you've got more than one input language installed, the "Key Settings..." button becomes enabled: click it. That opens the "Advanced Key Settings" dialog. Right at the top you'll see:
3. To turn off CAPS LOCK: [ ] Press the CAPS LOCK key [x] Press the SHIFT key