Navigation/arrow keys not functioning.

As of yesterday, my arrow keys simply will not work. There hasn't been a spillage, a drop or anything of the sort. They just stopped responding. No other keys are affected. Could anyone offer a solution or advice please?

Anything?

I had this happen to me suddenly also - woke up one day, signed on to my fave mmorpg, and found I could only turn right. Took it to an apple store and it was just a big piece of dust hindering it from pressing down correctly. The people at the store were really helpful and it didn't take long to fix it. They did say that sometimes it could just be faulty keys, which aren't hard to fix either.
Good luck, hope I helped.