I have seen that problem many times, and although I cannot tell you what keys are tied together on that keyboard's matrix, I can tell you that it is a very cheap fix.
We are going to take two things into consideration:
1. You have not spilled anything on this keyboard. If you have, then you will have to replace the keyboard and consider yourself lucky that it still boots.
2. The keyboard has not been physically damaged. (Missing keys, plastic plungers, bent, etc...)
If the keyboard has not suffered either of these predicaments then make sure:
1. The cable secured.
2. Nothing is on the contacts near the connection for the cable.
3. The cable itself is not damaged.
To remove the keyboard you simply need a Flathead screwdriver and identify the location of the 4 tabs that keep it in place. Right above the Del, F11, F5, and Esc keys!
Push the tabs back and then slip the screwdriver in the space between and pry the keyboard up one by one, and by the last one the keyboard will be out.
The cable for the keyboard will have a blue side and a white/silver near the tip. The blue side should be visible, and the black line should be hidden by the flip tab. There are two notches on both sides of the cable that make the cable fit snug in the connection. Check the 3 steps I mentioned and if you are sure there is nothing wrong then just consider the final step, which most people prefer, just to save time and effort; which is to simply replace the keyboard.
You should be able to find it for a pretty cheap price. If you look at the bottom of the keyboard, there will be sticker that has a DP/N: which you can use on eBay or amazon to find a new one for less than $20.
Good luck! Let me know if you need a pictorial guide on how to remove the keyboard.