Half of the keys of my laptop is malfunctioning: The right side of the keyboard corresponds to numbers and other letters. The left side functions normally.

When I connect my wireless keyboard, that one works flawlessly with the laptop.

I don't think it has anything to do with the problem, but the only two things that changed were that I switched back to wireless instead of wired connection to my router (secured) and I reinstalled the drivers to the wireless network card.

I want to know if buying a new laptop keyboard will solve this and if there are any other possible (cheaper?) solutions.

Press the Num Lk key and that should fix it!

Or it may be "Fn + NumLk" Keys pressed together !! to remove the number lock you put on...

I'm only going to be able to try that out tonight when I got home from my job, but just in case it doesn't work I'd like to ask one follow-up:

Wouldn't restarting the computer have solved it, if that was the problem?

It never did when I had the problem. I just tried it on this laptop again and my keystroke was just the Num Lk key. I too thought it was FN + Num Lk but not on this Dell Latitude.

Perfect solution: FN + num lock solved it.