Here are suggested solutions for you!
Unfortuntately, you and many others have this problem. I will point you in the direction of two "fixes" I have found.
Fix 1 is from Kenwood themselves, per the following quote:
"First try replacing the batteries if you haven't already. If that doesn't help, try resetting the receiver. Simply unplug the receiver, then press and hold the power button on the receiver while you plug it back in. Turn the unit on, and the display should say 87.50 to confirm the reset. If the remote still does not work, use a digital camera as an eye, face it towards the IR of the remote control. Depress any of the remotes buttons; you should see IR flash each time a button is pressed. If not then the problem is with the remote. If the remote works fine, then the problem is with the receiver. In order to determine the cause of the problem, I suggest you take the defective unit to a Kenwood authorized service center for evaluation. You can find information for authorized service centers in your area by visiting our website at www.kenwoodusa.com
The second fix involves some very simple soldering, and has been endorsed by many as the solution:http://www.remotecentral.com/cgi-bin/mboard/rc-theater/thread.cgi?3016%2C3
I hope this helps. Good luck and please let me know if this solves your problem!