after cleaning my puter, several keys now type two letters. any quick fix ideas?

I suspect the double letters produced are adjacent, either horizontally or diagonally (usually the second). This behavior is typical when liquid has entered the keyboard and is causing a short circuit.

Testing with another keyboard (with the original disconnected) is one way to confirm that the issue is with the keyboard.

If it is a liquid spill, sometimes extended drying can fix it. You can assist the drying process with a fan, but do not apply supplemental heat (such as a blow dryer).

You may want to refer to this link:

One or more keys on the keyboard do not respond

http://support.apple.com/kb/TS1381

This also includes what to do when keyboard keys do not work as expected.

Hope this helps. Cheers!

did each key separately.

You took the keys off? And you used a cleaning liquid? I'm not sure what to suggest at this point except that you might want to think about taking it in to your nearest Genius Bar and have them take a look at it. I'm assuming you're not under warranty any more, but at least they could give you an idea if/how mch it might cost to fix.

Another way to check this is by doing:

Click on the Apple logo at the top-left part of your screen then choose System Preferences. When you're inside the window, choose Keyboard. Under the keyboard tab, put a check on "Show keyboard and character viewer in my menu bar" and just close the window. You would notice a new icon appears in your menu bar, at the upper-right side. It looks like a pad with an asterisk. Click it and choose "Show character viewer".

A virtual keyboard would appear. Just observe if the return key would light up (color gray) as pressing on a keyboard key would be detected by this virtual keyboard. This would help us check the condition of your keyboard.

Could you be a bit more specific - how did you clean the computer? What did you use? Did you clean the keyboard and how? Same for the mouse and/or trackpad?