same problem on Yamaha RX-V650 remote. but it's quite easy to repair it.

1. open battery housing and remove the batteries

2. remove the screw located in the center of the battery housing

3. top and bottom shell of the remote are held together by 4 latches per side. the most fore and aft ones are located about 1cm from each end. pry them open w/ a small flat head. if you're carefull that will leave only tiny scratches, but it does take some force

4. once open, remove the insides and clean them from all the drinks and what not that has been poored over the remote (mine was full of... stuff)

5. if necessary, at contact spray or alike to the buttom of the rubber buttons

6. put it all back together again. you might need some new batteries as well. should work like a charm

PS: I made a repair guide.