For no apparent reason, my Acer notebook has suddenly started generating incorrect key codes. The problem seems to be confined to one part of the keyboard, the last three or four keys on the middle two rows. Keys are correct up to y, then the next four or so produce characters like @#$ (not sure of the exact ones). The row below in the same location does numbers, 1,2,3 etc. This seems to have started all of a sudden with no obvious cause. The keys are consistent, in that the same character is produced when the key is pressed. 

Can anyone offer me any insights about this, what could have caused it and what might be needed to fix it? Thanks in advance for any help.