Left and Right Arrows Not Working

My wife has a Macbook and the left and right arrow keys have suddenly stopped working. I've searched online and seen some conversations relating this problem to an application called Hyperspaces. However, I don't see Hyperspaces installed on her computer. I've also gone into keyboard shortcuts and reset to the factory settings. No luck.

Any ideas or recommendations?

That's really odd.

The first thing I'd look for is a mechanical problem. Pop those arrow keys off and see if something is under them blocking their function. Even a sesame seed can do it.

And, I found this on another forum:

....try to find out if it's hardware or software that's the problem e.g. does shift-arrow, cmd-arrow work? If yes, then it implies software.
Create a new user account (system prefs - accounts) and log into it, does the problem still happen? If yes, it implies it's hardware at fault. If no, it means that one of the preference files in your account is corrupt/broken.

Good luck!