Posts: 212
Threads: 80
Joined: May 2008
The cause could be a couple of easily fixable things:
1. Something (dust/particle) has gotten in between the contacts
2. Something sticky (like coke) has gotten in between the contacts and around the key.
First you could try using a spray-duster. You don't have to worry about it damaging the calc (just make sure you do you initial fire away from the calc in case there's some liquid in the tube).
If that doesn't work, you could try electrical contact cleaner spray. I've used this to fix the same problem on an hp-80 with excellent results (however I had the whole thing taken apart too. I don't think conservative amounts of contact cleaner will hurt the calc especially since its not close to the display. You may want to make sure you hold the calc with the display above the misbehaving keys.