Keyboard typing multiple letters at once?

I've had my MacBook for about 2 years now and have never had any problems with it, but a couple weeks ago I woke it from sleep, and discovered this issue:

The keys "R/T", "4/5," "F/G" and "V/B" each produce both letters when only one is typed. For example, when the word "frog" is typed, this is what appears: fgrtofg. Incredibly annoying, but the problem does not persist when an external keyboard is plugged in to the computer, so that is how I get by.

I'm a grad student and can't really afford to be away from my computer at least until the end of the semester. Has anyone ever heard of this problem? Any ideas for fixes?

Thanks!

Don't take this as an accusation, just asking as normally your issues are caused by this.

Did any liquid spill into the keyboard that you know of?

Also do you have a USB keyboard you could plug in and let us know if the issue is still there with the external keyboard?

No, no liquids that I know of. Computer was fine, closed on the desk, and woke up the next day with this problem.

Have been using a keyboard plugged into the USB, no problems with that.

Have you tried a Reboot? Complete power down and restart?

Yep, no change.