Sorry I am not a Mac user but it does sound like a key has become re-assigned. If it was windows I would say go to control panel and then to keyboard icon. Use the set to default option for the board keys. If you have a dedicated keyboard software installed, that would be the place to reset the board mapping. Hope this helps.
Just wanted to add my experience in case it will help anyone who comes across this thread who is having my same problem....
I came across this thread because my keyboard was typing "ik" every time I hit "i".
Turns out, the keys were still*physically* attached to each other--apparently the keyboards are manufactured in a sort of continuous sheet and all the keys are connected to each other. Somehow my "i" and "k" keys were still stuck together like with the original plastic not having been separated at the factory.
I snapped them apart using a paperclip, and now the keyboard works fine.