That can be a very frustrating situation. Please don't be angry, or insulted, if I suggest the most obvious:
Check, and "double check" the condition of your capslock key.
I'm not trying to be condescending here; 95% of such problems with my users result from haviing inadvertantly/accidentally hitting the caplock and not realizing it.
I've been doing this stuff for years, and did this to myself just days ago..locked myself out and thought I had "big trouble' till I finally checked that